As a professional accidential teamkiller/TK-victim, I decided to start a topic, so that everyone can share their best tricks how to avoid pumping your own guys full of lead (or fire/HE/AT/water/mines etc.)
Some of my tricks I use
1. LOOK AT THE MINIMAP!
It is annoying when people storm in friendly houses or bunkers and manage only to finish off a couple of friendlies. A quick peek at the minimap may sometimes be even better way to identify friend or foe than uniforms.
2. 3D map info
Yes, 3D map is less informative in FH2 than in vanilla-BF2, but still it is a good way to check who is who in the battlefield. Especially the S-Mines shoud be acknowleged by this way.
3. Flamethrower
Caution! It's hot! - Flames will kill anyone and running in front of a flamer is a bad idea. Also keep in mind, that flames fly in an arc and they do some sort of splash damage so don't W+M1 with it, save it for Team Fortress 2.
4. HE rounds
When in a tank, be careful and aim steady. If infantry is charging at a building, use your MG to provide cover.
5. S-Mines [AP-mines]
Placing them demands strategy, so don't be a douche and place them behind every corner of the house. It might help you to hold a building when you are alone or you are swarmed by enemies, but remember, that S-Mines basically deny all reinforcements untill all of them either blow up or disappear. Keep at least one path clear, when you try to defend a house.
6. Uniforms
WW2 was one of the last wars, where general diffrencies between uniforms were notable. Take your time to learn similarities in dressing between fellow soldiers, if you don't seem to know who is who.
Some easy points
Germans - Stalhelm - From Somme to Berlin, the German Heer has used them to keep their boys safe.
British - Broadie - From Ypres to Palestine. Hard not to notice or keep in mind.
Italians - Reddish Brown or light dirt-coloured uniforms
Americans - Olive/Limegreen uniforms and helmet. a GP Standard uniform for those GI's.
ANZAC - Same as the British.
Here are my tips, where are yours?