My two cents for tanking.
Rule #1, DON'T USE WLAN!
If you are, you would usually come head-to-head with a Panzer that can kill you with a single shot and the infamous "YOU HAVE A PROBLEM WITH YOUR CONNETCTION" pops up, and when it goes away, you're dead.
Rule #2, Hull-down positions
Hiding that tall Sherman aluminium foil hull will increase your chances of surviving tank vs anything-else- that's-not-airborne combat. The turret is harder to hit, since it's a rather small target. Note that this also applies to tall self-propelled guns. (read: marder-series)
Rule #3, Smoke shells are not rubbish
When attacking, fire smoke shells to create defilades from anti-tank guns. Also, if you get hit but are still burning, fire a smoke shell between you and the shooter, then retreat to a not-obvious direction, meaning: don't go backwards. Move behind the nearest cover and repair, which leads to the next rule:
Rule #4, Take an engineer kit
Don't take limited kits with you if you decide to go tanking, since you'll block the kit from other players. Also that wrench comes handy if you manage to bail out of your tank before it's destroyed and fix something, say, a PAK gun to avenge your tanks fate. The explosives are useful, if you know you can't repair the tank in time or you are out of ammo and other people decide to be pillocks and not get an ammo truck, blow the tank up, so it spawns faster.
Rule #5, Tanks have different roles.
If your tank has a slow turret or it doesn't have one, defend with it. Anticipate the enemy's movements and wait in their flank to maximize the potential of the gun. Also applies to Tigers, but they are better in fire support role with their heavy armour. The Churchill, however, is best used as a plow. Lead the attack with your heavily armored fast turreted tank. If a defending tank shoots at you, the armor can take it, then just blast the guy. StuGs are different. Their low profile makes ambushing easy. wait under trees for that sherman to expose himself. Also works in bocage country. Sitting low, you will be able to see targets sooner from under the branches than the opposing tall Sherman can see you.
See drawing: