1. behind hedges- there will be "gaps" for you to shoot through, for example, in luttich, near farm, the area I marked could station a tank and watch for any incoming stuffs, usually your enemy would never see who's shooting at them.
In totalize this could also be exploited by the defending germans, tanks hiding behind hedges could shoot through the small "window" of each row of hedges, a stug positioned like that could be very difficult to be taken out except by air.
This method could be used extensively in goodwood, an evil method!
2. behind a big piece of rock/slope/wall- it is the more practical method of camping in the desert maps, when you only show your turret your enemies can't really hit you that easily.
3. hiding behind vegetations- similar to 1, since freelook is "higher" than your gunsight and your tank, so, you can watch your enemies behind the vegetations without the chance of being discovered, simply drive out and shoot your enemy when you sight one, if your skills are good enough, maybe you just shoot through the vegetations. The marders, though weak in armour, could employ this method effectively since the gun is high.
4. freelook glitch sniping- nothing special, maybe just an exploit instead of a method. Not recommended.
something you need to pay attention when camping is your engine noise, which would reveal your presence to nearby enemy infantries, not a really good idea to camp in normandy without securing the flanks.
also, when your enemy don't see you when his turret is pointing at your camping place with "uncertainty", don't fire at him yet unless you are confident to take him out with that shot
it'd be a good idea (quite gamey though), to switch to the passenger seats and hear for enemy engine noises, everyone want to flank that camping bastard, so you won't have a heart attack when your tank is suddenly blown up
some fundamental tips these are, but nevertheless I want to show these as I don't play much now and won't worried of getting owned by campers.