There's a few of things you should know of the basics:

*Considering early game & Normal/Hard difficulties since Hoe is fckd up without high level perks and good coordination :'( *

1. Running faster with knife is back!: In KF1 you run faster with the knife unsheathed, on the second game this mechanic disapeared and it is finally back! , mark this as it would be very important later.

2. Destroy cameras/electronics: I think this was on the tutorial, but it's kinda useful since it gives you electronics/bio steel for weapon upgrades and 5 dosh each one destroyed (the money doesn't share with the team, the materials do share), if you go arround the map destroying you can win a few extra dosh on the wave prep meantime; this work for usable items, ammo refill and armor.

3. Try to get used to slide/dash: It may seem situational, but this mechanics are way important, you can dodge a lot of attacks and move way faster depending on the structure you do this, I'll fulfill this later tho but keep that on mind.

4. Save gadgets for special occations (at least on early perk lvl): As you might know different perks have different gadgets cooldown, some of them may reduce cooldown with perk level ups, etc.
But usually those are really long if you're not ninja, so, for example, try to use the perks smartly:

-For clearing small zeds every perk works like a charm

-For big zeds:

Comando dron deals a lot of damage to them, you usually need 1 full dron activation to take care of 1 Flesh/Scrake (At least in hard)

Engineer's sound blast usually works good for Fleshpounds due to the soundwave weakness, but it can knock down a Scrake just fine (after 30 I think this does way more dmg so I wouldn't know on this case)

Sharp usually makes a lot of damage on crit points and kinda stagger, so you may support team and yourself with this!

I think Ninja gadget usually stuns big zeds that you grab into, at least if they're not enraged. Use this gadget too if there are annoying small zeds arround the big ones since it release a shockwave after grappling !

Use med/firebug to support your other teammates and deal extra dmg, but I would save those for another situations (or not, your call).

Also with each upgraded perk you may found another uses for gadgets, find your way to play!
but on early this works fine.

5. Weapon Upgrades: As you may seen you can upgrade weapons with a lot of items, and also each one of them have a passive that you can unlock on the last tier. About this:

First thing I would recommend is to upgrade the medic basic pistol to the insta heal upgrade max tier since you can buy off perk weapons with every class. This is extremely useful for every match and if you have no medics you can just heal everyone and win dosh on the process. Just remember if you have a little extra money try and buy it!

There is no need to fully upgrade a tier 1-2-3 weapon: you may see there are weapons that uses different playstyles like the pyro explosive wpn, you can use that as a flame thrower, etc. and there are upgrades that favors one playstyle more than other, or weapons that have accesories that just highs up the price of the gun for the wave utility - example - You don't need a very expensive itemized starter weapon for starter wave, neither one fully moded weapon for waves 2, etc. Try to focus on modify your weapon based on the lack of stats of this one.

For boss wave: It's highly useful to mod your weapon fully and max out everything, but after this choice find your desired passive. See, when you create an accesory you can inmediatly see the passive the accesory gives you for the weapon, if this passive doesn't fit your playstyle you can recycle the mod and create it again untill you find your desired passive. Try to do it before upgrading the mod so the recycle and material loss doesn't hurt that much :')
-Also, you may not be able to buy a way expensive tier 4 weapon with you having max tier armor, so, sometimes you need to sacrifice the last tier armor upgrade, or maybe sacrifice buying some grenades.

6. Buyable tools refresh after opening the shop pod, and those have a limit per wave: Situation -> You finished a wave and you didn't used your item, such as ammo bag, shockwave trap, etc. so you opened the pod and you realize you didn't use those, you try to waste them to buy another usable but the shop display "Wave limit".

This happens a lot, so if you haven't used a support item such as medic bag, etc. use it before opening the pod, so you can refill another item (or the same one).

Also quick reminder, ammo bag replaces 1 grenade and almost half your total ammo!

7. Read the mutations so you can addapt your playstyle : You may have realized that some waves have mutations such as hellfire, fodder, etc.

Try to assemble a plan to survive those, some examples:

Fodder -> A lot of crawlers, buy not so ammo dependant weapons or carry ammo bags, also firebug is buffed, so try to rely on that class to kill small zeds and you worry about the big ones.

Hellfire -> A lot of husks, cover yourself on interiors, preferable with no straight corridors and an obstacle or two to cover from fire. Try to shoot at the tank of the husk, specially with sharpshooter weapons or ap/explosive ammo classes.

Acidic assault -> Lot of bloats, I usually like to wait for them to inflate and shoot them, it's kinda easy as they don't cover they head and you only need a few bullets on the red spots.

The Horde -> Lot of clots/cyst, and enraged zeds (careful for Scrakes on this one as they may grapple you). You may waste a lot of ammo tho, and they come from every angle, so try to rotate if you're alone or assamble with the team. Or rely on ninja since cut dmg is buffed.

Slice & dice -> Lot of Scrakes and gorefasts, good luck :') , ballistic weapons and shock traps may do the trick. Try not to hold in one place if you're not sure of your team firepower.

Pounded -> Lot of Fleshpounds, I personally found this easier than the one above since it's easy to blow up Fleshs with explosive weapons and gadgets. Just try to not enrage them all and rely on the Ninja parry if you have one. Shock traps works as well.

The one with the sirens I don't remember the name heh -> Lot of sirens, a little hard to kill with ballistics, try to blow them up or cut their neck when they stretch it.

8. And finally, learn to parry: If you're new on the Killing floor games you might think at first sight this is only a ninja/meele user mechanic, but not really, everyone has a knife and you can use it to parry a loooot of attacks, so, try to learn the patterns for the important dmg zeds and I'll cover this later on the next topics.

Oh boi my favorite part of playing is to discover new ways to survive/kill things.
There you have a few tricks/guides I've compilled:

1. Run Faster: One of the esentials; as I covered above, learning to dash and slide is way important, one of the reasons is for this.

Keep in mind you can dash diagonally, what does that mean? while you keep W + A or D you can dash foward, advancing a little more distance than walking or running. This have a cooldown of something like 1-2 seconds, but I like to guide myself with the character footstep sound, I always count 4 and dash again.

To this, add up the knife movement speed mechanic and for the last part the slide one. On stairs, the slide animation is extended, so, start running from the map with the slide-knife mechanic and if you see a stair slide and cover more area.

You can add up some speed boosts like the Sharpshooter perk (the one when you recieve damage you run faster), the Comando syringe one, Engineer speed after killing, etc. If you play Ninja you'll get use to it pretty quick.

Now considering this, you can use this mechanic to outspeed some bosses like the impaler, or the crawler queen after the second phase. I found this trick way important since you can kite the boss and shoot when you're on a good spot.

2. Know where to use the support consumables: I've seen a lot of people on the boss wave specially throwing meds, ammo bags on one spot. I don't say it's bad since every match is different, but I really like to save one to the late wave. You never know when you have to leave one spot (wether big zeds gather and you have to run from there or if the boss dominate that spot, specially an impaler chase). Who knows, may save a match.

3. Parry bosses/big zeds: Continuing with the parry mechanic, it's another esential since it can save you from a certain death. As I said before, try to learn the big zeds patterns, since you can use the parry to block almost all the damage and also knock yourself backwards, this may save you from gathered zeds and gives you a distance advantage.

With bosses it's kinda the same, but there are some bosses than have different and chaotic patterns, specially if you have explosives/fire on your team since it can block you sight. The best parries you can make are:

Impaler: 2nd phase it's the easier, they have very predictable patterns (try to avoid their missile animation before trying this), specially the one where the do the gorilla chest beating, try to cover distance as they will roll and after the roll they will strike, I usually like to outdistance them, but if you're on a position where you can't escape & if you're on a right distance you should be able to parry that.

Crawler Queen: Harder to parry on my opinion, the second phase it's the easier too. In the attack where she teleports after she spawn the baby crawlers she will rise from the ground, if she rise towards you, try to parry her on the last frame and you should be fine (also outdistance the little crawlers, nasty things those)

Chimera: It's kinda unpredictable, I like to parry it on the second phase too, it usually chase the further player, and when he teleports it usually attacks inmediatly, so if you time the teleport and the attack you should be fine!

As a summary, it's only practice, and don't be afraid of parry, the knife also have a little defense that still reduces a little damage if you block an attack!

4. Some bosses tips:

Impalers: If the server is full of players 3 impalers will appear 100%. I found the best tactic is to split; 1 player lure 1 of them, 3 players stays with one and the remaining 2 players fight the last. The single player can lure the boss till they've killed one or all the other impalers, or you can fight it alone if you're brave enough. BUT IMPORTANT, keep in mind the position of the other impalers, and try not to go where your other teammates are fighting, know the map and you should be fine. What else? parry them, on the second phase if they do the missile launch animation just break sight and it will cancel it, so try to avoid straight corridors. Aim for red spots and if they break they'll be firing less missiles and you'll reduce them attacks to only meele, or 1 non-that lethal missile (but still hurts). Last thing is if one of the Impalers dies, you'll win money, so you can refill on the pod if you're out of health/ammo.

Crawler Queen: This boss is kinda hard to dodge, specially when it makes the jump attack, so if you're an squishy class try to keep your distance. When the boss spawns shoot inmediatly to the big insect head it has, I like to carry freeze affection bullets or so since it can be freeze for a sec or 2. The first attacks may be shooting yellow eggs(? to the ground near you, but those are explosives and slows you down if you step on them, so if you have dps weapon or aoe too, try to shoot them before keep shooting at the boss, as Ninja be careful if there is no medic. Triggering the 2nd phase shouldn't take long, and this is where it turns very annoying. When the boss triggers the 2nd phase animation, use all your resources to do damage since it would be exposed for a few seconds, I like to use Comando dron and throw grenades at her (save at least 1 grenade), or release big fires as pyro.

This is when she start using the portals and spawn the little ♥♥♥♥♥, so, depending on the class try to save the aoe gadgets for this situation, if you can try to gather together, but be careful when the boss emerges. Also, shockwave traps seems not to work with the little crawlers, so if you can activate the turrets on this scenario.

Chimera: Not that hard but still can catch you on a bad spot. First phase aim for the head and shoot with everything, sometimes it will chase someone and aproximate fast, so be careful. Be aware of the orange spots it throws, since little zeds (the ones with the red spots on face/belly) will spawn from there, so aoe/dps classes try to focus on that. After the second phase is triggered, it will create a purple field and explode, so don't go near him! , it usually teleports after this animation, so be careful, it normally teleports to further players, so if you're alone keep an eye on that, and as I said above, after every tp it seems to attack inmediatly, so you can try to parry that. Oh, and it will shoot a lot of orange spots, so be aware of little zeds.

5. Big zeds like doors: When big zeds spawns, I think 100% of the time they'll destroy doors, even if they're open, making a big hole and sometimes opening the area. Use this to cancel their animation, specially when they're chasing you or enraged, I think you can pass through one of this doors and the zed will destroy the door first after continuing with the chase. Also, I think some bosses do the same, Impaler maybe? I don't remember honestly but keep that in mind!

6. Activate turrets faster: This one is very useful, after you've activated a turret and the cooldown ends, you can dash diagonally and press the activation key (E default) at the same time, it should activate the turret instantly, so, if you're running and don't have 3 seconds to activate a turret, try this.

7. Invulnerability seconds, damage reduction and more uses: You may have seen some perks that gives you seconds of invulnerability, or damage reduction (like ninja or engineer gadget perks), etc. You can use this to gain time, revive teammates or tank big zed/bosses for a while. Comando have one of the invulnerability perks and have a pretty reasonable cd, if you use it on early-mid waves this may be used again on boss wave, so, if one teammate is on a tight spot I like to sacrifice myself to reanimate him, usually I don't loose anything and you can always use a grenade/gadget after reanimation to clear your path. Another uses are where the boss is low on health, there are a lot of matches that ends before the boss is killed and in the last minute due to the boss aggro, that's when you can use this perks to tank and win seconds for your team. My favorite is the Engineer's gadget damage resistance, it can lure Impalers and bosses to you, and as long as a medic is healing you you're way inmortal, just keep the last gadget ammo to extend the duration as long as you can.

8. Gadget Invulnerability: I've noticed that when you use wether Pyro or Medic gadget, you win an invincibility frame as long as the animation last. I've found this useful on a lot of situations, specially boss ones, you can tank an important hit if you're fast enough, or get yourself out of a situation. Also notice that the gadgets can be activated on the air if you jump, so you can shorten the animation frame if needed.

9. Ninja's brutal dual katanas damage/Charged attack dash: I don't know if you've noticed, but dual katanas strong attacks (with the electric ammo on) can literally 1-2 shot Fleshpounds, specially if they're modded.
If you attack right into the Fleshpound chest you can execute almost instantly if you get a good strike, and almost kill Scrakes inmediatly if you aim for the head. This is extremely useful for the team, try to go straight to the big Zeds (and also execution releases a shockwave that clears, so if you're holding it works amazingly). Also, you can dash foward while charging every meele weapon, keep this in mind to strike or dodge while attacking.

10. Off-perk weapons: You may noticed that class only have a very small variety of weapons, but the good thing of this game is that you're not limited to class weapons dmg, all the base damage is the same for every class, so you can create off-perk class moded weapons that can adapt to your playstyle.
For example, the grenade launcher; you can put confusion ammo for Medic, or incendiary ammo for pyro, etc.
I'm willing for future weapons to keep the same freedom, so give it a try.

11. Cancel reload animations: You have the clasic bash cancel, but the fastest one I've found is climbing on a surface like Convoy's jeeps, etc. Once you reload and the ammo shows in the hud inmediatly jump and hold space to a high surface. If you're using slow reload weapons like grenade launcher, Vulcan, Ifrit, etc it may be useful !

12. Ninja Bloat kill without explosion: As ninja, if you don't want to be covered in acid everytime you fight a bloat you can wait untill it inflates and just as he raises his head you can meele him either in the head or the body to cancel its spit attack


And I think that'll be all for now, If you have more tricks leave it on the comments, cheers!

Those are things I like to do to improve the match / team profit:

-Buy Medic pistol off-class: With the modded weapon you have an amazing reliable healing tool for the team, so if you have extra dosh always buy it (with the insta-health mod if you can), it literally save matches.

-When you choose loadout or you join later, try to change the equipment to the multi-tool and activate everything you can before opening the pod shop (for the thing explained above on the guide). Specially ziplines and armor lockers for later.

-Parry big zeds for your teammates; If you see your teammate struggling with a big zed try to make the zed aggro to you and block the enraged attack, then gather or flee.

-Save shock traps for some situations: You may not wanna use all the shock traps inmediatly, since they can be activated by small zeds. Try to save them for really tight situations (too many zeds in a close space, more than 1 big zed coming for your team, etc).

-Use the traps: there are traps like fans that are very useful to defend an area if a lot of zeds are coming from every angle; also, fans can one-shot big zeds but they become useless after that. It might save you some day.

-Leave an ammo bag next to the shop pod; sometimes refill and grenades are way expensive and the dosh can be used in other stuff, so it may be helpful for your teammates to be able to save some dosh replenishing the ammo with the ammo bag instead of buying it.

-Ping the boss/bosses; with the same button you open the communication tab you can ping, it's always useful to ping bosses to know their location!

-Leave equipment on diferent parts of the map, specially on the boss kite route to make it profitable on the boss wave

Feel free to leave your tricks or wathever you want that could help people, cheers!