P4D is the easiest, it is grey/blue with a stub gun.

P3F/H are the same, you can tell the difference by the sound.

Stug3b/3g has no turret, they are also lower, 3g has a mottled green/tan armour colour, stug3b has a grey/blue colouring

P2 is the easiest, it sounds like a milk float as it approaches, back of the turret for this one, I believe you can kill this with a rifle if you know how.

p38t is the little brother, fast and agile, I hate this one as it’s tough to pop due to the placement, but you can tell which it is because it looks small like a P2 but without the low turret that the P2 has.

Clown car (aka 232), easiest to kill and can definitely be deceased with a rifle. I enjoy popping the tyres on this one, eventually it can get itself in a spiral spin and be totally undriveable which is amusing.

Infantry sounds
http://www.youtube.com/watch?v=j4BDgXus4lU