World of Tanks is an game based off of detection, camouflage, penetration parameters, damage and line of sight to make for a compelling game. This particular post will be dealing with one particular type of tank, the Tank Destroyer.
The first and most important thing about playing a TD is knowing that you are a long range hidden attacker. Remaining hidden is purely about reducing the enemy's view range. This is achieved by three different things. The first thing affecting view range is obstructing obstacles between you and your enemy. Bushes and trees that have not been knocked down will reduce the range at which you can be spotted. The second thing is Tank activity. If your tank is driving hard it is easier to spot then if it is sitting still. In addition firing a shot will significantly increase how far you can be viewed by. The third thing reducing your enemy's view range is the camouflage skill of your crew. This can only be trained by a 100% crew. The other half of the equation is increasing your view range. This is achieved through buying modules that increase your view range by a certain % or by increasing the % of the commander of your tank. It is strongly reccomended that you at least buy the 75% crew training before moving up a tier as tank destroyers are handicapped with a bad crew.
One note worthy point is that rotating your tank is considered moving while rotating your turret is not. This means that TD's able to rotate their gun are generally better at staying hidden then their fixed turret counterparts. Tank destroyers are also very accurate tanks so be sure to aim for their tracks should an enemy be trying to close in on you. In addition always keep and eye on the number of enemy artillery up, their primary job is killing TDs and Heavy Tanks. Should an enemy tank detect you and begin firing you need to quickly access you ability to escape vs kill the enemy first. TDs have decent frontal armor and can usually take a high explosive shell to the front just don't let them hit you in the sides or back with a high explosive shell or you're done. In addition once the enemy has been killed it is advised to quickly change positions as artillery will soon be aiming for you.
Guns and Ammo
TDs guns come in two varieties. These two varieties cater to either high damage or high penetration. High damage guns are used for TDs that aim to take out quickly advancing scouts and for flanking enemy mediums or other TDs. High Damage guns are not meant for being fired at frontal armor or heavy tanks however can still provide usefulness against heavies when using high explosive rounds to damage their tracks allowing allies to finish them off. High penetration guns are designed for putting a round through the frontal armor of enemy medium tanks and the flanks of enemy heavy tanks. Golds rounds are always the best if you have them but for standard AP rounds and HE rounds you use them depending on the situation. Generally use AP rounds when encountering mediums and heavy tanks or TDs that will likely be facing you. HE rounds are used for dealing damage to modules such as tracks and one shotting things it can penetrate, meaning Arty, TD flanks and Light Tanks.
In general TDs require careful planning and paying close attention to where everyone else is and where then enemy is going. Relocating to a place where you can stay hidden and keep your advantage over them is the key to victory. My personal best is 9 kills in one match with a Marder 2. Have fun beating my score.