This guide is intended to give new tankers an insight into the role of tank destroyers and the tactics employed. It is not a guide on gameplay mechanics etc. Neither is it a guide detailing the differences between TD types and models. I will cover those topics briefly where required. Throughout the guide I will be using the german TD's as examples, though most of the content is also applicable to the yank...errr....American tanks too.

Tank Destroyers

Possibly the most misunderstood unit in the game. The clue is in the name guys but just because it is called a tank destroyer, this does not mean that it is uber-powerful and capable of killing all opposition with ease.
German TD's have no turret, and the main gun has limited horizontal and vertical movement giving it a limited field of fire and vision. The TD is an ambush predator. It is the sniper of the tank world and does not operate well in an overtly mobile role. If you ignore this and try moving with the main assault and operating as a tank does, you will die. Simple as that.
The TD has one main role and that is to kill tanks. As an offensive weapon platofrm it is severely restricted. When used defensively however, it can have a devastating effect on an enemy advance.

Role

As mentioned above, your role as a TD is to kill tanks. How you do this is up to you but if you have even an ounce of sense you will use this vehicle as it was designed to be used. You are able to hit targets across the map and still do damage, use this to your advantage. There is absolutely no reason for you to be iin the front line trying to skirmish with the other, often lighter tanks. They will run rings around you and if they get your sides or rear, it's game over.
That's right! If you didn't know, any tank has stronger armor to the front, less to the sides, and even lessto the rear usually, and the german TD is no exception. ALWAYS keep your front to the enemy, and the easiest way to achieve this is at distance where any adjustment you need to make to your facing are minimized.
Now the most important defensive measure iin tank lore, any tank. And that is the principle of the hull down position. Every tank should attempt to achieve this whenever it is stationary. And the TD is stationary a lot. Hull down involve positioning your tank behind a terrain feature so that as little as possible is exposed. In fact only enough to offer a field of fire is best. With a normal tank, they aim to just have their turret exposed, but as a german TD you don't have a turret, and you do have a low profile, but still ALWAYS attempt to get hull down when possible. The less of a target you offer, the less the enemy can hit. Check out the image below of a german Ferdinand TD in hull down. He is using the lay of the land by parking on a small reverse slope to keep his profile minimal whilst still exposing his gun.

As mentioned, your TD is the sniper of the armor types. So using other cover such as bushes and/or woodland is also viable. If you can combine this with the hull down position then you are well on your way to being a great TD player. Rock outcrops are also useful but beware of using any that are at the top of a slope, you will silouhette yourself against the sky. If you must use the top of a gradient, try to use one that has some form of terrain behind it (from the enemy perspective) or you will be too easy to spot. Often it is best to actually hide in front of cover. Those grey rocks for example can help to break up the outline of your vehicle, making you harder to detect, hopefully long enough to destroy your unsuspecting target. Which leads us onto the shot.

So, there you are in heavy cover, your in a hull down, you have a great field of view and fire. Your target is unsuspecting and in your sights. So now we fire? Do we 'eck as like! We wait. Your first shot is going to be your best shot. You want to make it as accurate and devastating as possible. After that shot, your enemy will be evading if he is still alive, or running for cover.

Bring It On.

Yup, let him come on. The savvy of you will have used your common sense to position yourselves slightly off of the center of advance. So you wait until a side shot if at all possible. If a side shot is looking unlikely then you want that guy to come as close as possible before shotting.
This is a balancing act. You do not want him so close that he will be able to engage you in a manouver battle and you dont want to leave him alive long enough to cause too much damage. So assess the situation, if you are in danger of losing the shot, if the enemy is too much of a danger to your troops, or you are in danger of discovery, then take it.
All the time you are tracking your quarry, keep your range finder tuned. To do this, set the sight over the target and press space. Do this frequently as the range changes, and do it again right before shooting. Many an opening shot has been ruined by an overly keen tanker not remembering this simple thing.
Soooooooooo... He shoots! He scores! GOOOAAAAALLL! But wait! We're not done yet, and neither is he. Most likely a second or even third shot is required. Here is where your gunner badge comes into play. If you don't have it equipped, you should have. Reload speed is your new best friend. Once that first shot hits, he is going to be looking for you. You now need to finish him before he finds you and make good your escape. Which leads us to the next section.

Your target is no more. A smoking crater strewn with twisted metal. Time to celebrate and bask in your own awesomeness right? Errrr NOT!! Time to skidaddle, hot foot it, beat a reatreat.
Remember me saying you are the sniper of the tank world? Well just like a sniper, you need to relocate once your position is compromised. And unfortuantely, due to the ridiculous implementation of a forced kill-cam, you have just been compromised (I am not sure if the camo badge applies if you are in armor. I hope someone can clarify).
If, and it's a big if, you are in a position that gives such an advantage that leaving it would be detrimental, then by all means take a risk and stay put. However, always best to move. Now be sensible here, do not start rolling forward and turning your TD. Even now there could be an enemy TD or tank zeroing in on you. Reverse, keep that front to the enemy. If you used the example of our Ferdy in the previous section to get a good hull down position, you just reverse back away from it and out of sight, then make your turn. DO NOT return to the same place too often if you can help it. You need to learn the good spots on each map and that comes with time. Once you have noted several, switch between them and do not use a pattern, randomize it.

So, now you have stalked a target, postioned yourself for the kill, destroyed it and escaped in one piece. So now do you bask in your awesomeness? No, not yet pal. Now you worry about infantry, because you can guarantee there is at least one suicidal rambo or -even worse- one good patient tank hunter gunning for you.

Yeah Infantry are your worst nightmare, more so than tanks. Due to you limited vision, slow move rate and manouverability, you are a big fat juicy worm on a very large hook to them.
Situational awareness is a must. One sure way to acheive this is to have a second crew member equipped with binoculars and a pistol. He deploys outside the vehicle and is able to scan for targets and approaching threats with a wide field of view. He can not only spot targets for the main gun, but can also spy out those infantry. This is fine when in a defensive position but not when moving. Speed is your ally then. Do not bother trying to use your mounted MG unless the infantry falls within the field of fire. You will waste time and speed trying to turn and get a shot. Also, while you are focused on one soldier, there could well be another on your blind side. So move. Most infantry want an easy kill, so they tend to give up after a few minutes. Not all mind you. You will just have to hope. Asking for infantry support in chat is an option......... It's an option that the infantry will ignore too. As I have always said, the XP reward system encourages self centered non team oriented gameplay from most players.
If all else fails, use surprise. Leap out the vehicle and engage the guy personally. If you seem to be attempting to escape and evade him he will likely not expect it.
Infantry are a pain, and in the german TD's you are extra vulnerable to them. Minimize the risk initially by using the techniques for cover and positioning.

The german TD is not only a great "tank". It is immense fun when you get it right. There is a great feeling to be had from destroying an enemy tank without him even knowing what hit him. I will just repeat one point again in case you still haven't grasped it at this point. You are NOT a tank and should not attempt to operate as one at all. Don't say I didn't warn you.
Good luck, and above all, have fun.