1. Most importantly: ignore quests for a while, and just do basic contracts until you feel comfortable, have a good reserve of money and spare parts. Storyline doesn't pay. Basic contracts around starting system, on the other hand, pay a lot. When picking a contract, sort by payout, and don't forget to check origin system - some contracts start in another system than the one you're in.

2. Don't try hauling more than one contract at once. "multiple trailers" means one contract with pre-assembled trailer combo, it doesn't mean you can just combine trailers by yourself. That may sound silly but it costed me a fortune when I tried. Accepted three contracts, failed two, had to pay a lot of fines for that. Judging from forums, I'm not the only one.

3. Game time is 1:1 scale, one minute per minute, but every warp costs you one hour or more (depending on distance between systems). This means there's no need to rush, even if you're late. Whatever time you spend inside system is nothing compared to warping.
This also means that "just in time" contracts are generally not worth it. You arrive one hour early and now you have to either wait ONE REAL HOUR doing nothing, or warp back and forth and now you're late. But if you find yourself in that situation, at least don't forget to dock while waiting, you don't want to waste one hour worth of batteries.

4. Speaking of batteries. Your truck eats them like skittles, and you always need more of them. So every time you pass near the store, dock and buy the batteries if you are low on them. And sell back empty batteries - they are still worth decent amount of money, especially if you keep some charge on them - 1% battery is worth much more than 0% one.
You will also eventually need to replace your air filters. They are expensive (2500-3000 each), so best to save money and stockpile them in advance. Some are usually sold in Medusa Six system. Percents seems to be misleading - check HP instead, they should consume around 450 hp per hour (split among all filters). Same as batteries, don't throw away your old ones - sell them back.
Oxygen production is affected by average %/hp of filters. Thus, you can prolong life of "bad" filters by installing them together with fresh ones.

5. Battery economy. Turn off all lights (unless you need them). Set blower to low (but keep an eye on the interior temperature, turn it back up if it starts changing). That will greatly reduce main battery use. Another battery you can optimize is suit charger. It only uses energy when recharging your space suit, and it uses a lot of it, so if you just used your suit and won't need it again, keep charger offline until you dock, then turn it on again, and it will charge using free dock energy instead.

6. Put all your stuff into containers (buy more containers as well). That will prevent it from taking damage when it hits walls. You can also put containers on shelves and open all lids, that will fix them in place. Now you can safely turn off gravity, and that's one less battery to maintain.
Some items that can't be put in cases, can be locked in place by putting them between two cardboard boxes with open lids.
You can also lock some of the stuff in the airlock (but you'll have to remove it first if you want to go spacewalking). This won't prevent damage, though, so only do that for items that don't have HP (like mining charges or traffic cones).

7. Fuel economy. This game has newtonian physics. This means accelerating uses fuel, but cruising doesn't. By default, you have "drive assist" turned on, and that kinda hides that fact - you turn and your direction changes too, but what actually happens is that your truck uses side engines to change direction, using fuel every time you turn. If you're flying straight for a long distance, you can turn drive assist off, and now you will keep going same direction and speed forever, not using any fuel at all. But unfortunately, you can't strafe manually, so you will need to turn it back on when it's time to turn.
TLDR: fuel is used when accelerating, braking, and turning. Try to minimize it by driving straight as much as possible, and disabling drive assist when you can.

8. Trading is a good side income. It requires having some money to invest, though. Every system has price modifiers you can look up on the map, so buy stuff where it's cheap and sell it where it's expensive. Not all stuff can be put into containers, so for some you will have to turn on gravity to avoid damage - keep that in mind.
Even better is salvage. Once you unlock scanner upgrade (Moon Baby quest line), spam honk everywhere you go. If you see a beacon, go there and pick up free stuff! It's very lucrative (most profitable activity in game by far), and can be combined with trading for even greater profits.

9. Speaking of damage, here's a small tip. With gravity on, when you place stuff on the cabin floor it's dropped a bit, and that makes it take a bit of damage. Instead, place it on the dashboard (or bed) as low as possible, this will minimize fall damage.

10. And the last tip. Don't forget about screens. When flying through debris, I usually set right screen to bottom forward camera - helps to check if I pass over obstacles. If you have shutters down due to solar flare, you can set left screen to forward camera as well - it will be same view you have from your seat.
When just cruising, I set right screen to batteries/forward-bottom camera, and left screen to left mirror or docking camera.
When docking, use the docking camera (obviously).
When hauling multi-trailer cargo, set left and right screen to side mirrors, and try to keep your trail from crossing middle of the screen.
Use zoom button (Z) to see debris better, and disable system alerts (switch on top panel) to get rid of "WARNING: DEBRIS PROXIMITY" that obstructs the screen.

Kecske posted a guide containing a full game map, with all information from map screen - including jump times and blackmarket locations, I suggest checking it out:
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3326495179
Mike Takumi made detailed analysis of income and expenses, if you want to know exact numbers check their forum post:

Originally posted by Mike Takumi:

That makes the LOW end of expenses at average price
Cheap batteries: $6,195/hr, $6,835 with grav (see, $60 for lights is nothing)
Medium batteries: $6,653/hr, $7,505 with grav
Big Bats: $8,265/hr, $9,865 with grav

Originally posted by Mike Takumi:

So you're roughly looking at around $10,000 an hour in income. Which all together means your possible profit per hour looks like this.
Cheap: $4,762/$4,186
Medium: $4,350/$3,583
Big: $2,899/$1,459