Rules 1 - 25: Never take a teammates tank unless it's offered to you.

Rule 26: Keep the radio chatter down and learn the keys you really want: it's very irritating to listen/read while someone is pushing all the quick chat buttons trying to find the one they really want. By then your message is lost anyway - no one is paying attention.

Tip: Look carefully at your target - if it's a Nod vehicle, does the "tag" show Nod also, or did one of your team appropriate it from the enemy. I see lots of guys wasting time shooting the tank I just stole, when they could be doing something useful, and I can't get out to repair my stolen goods while the new guys are hosing it with their weapons. If you aren't causing any damage - maybe it's because your teammate owns it.

Welcome again, and read lots of the forum messages, there's lots of great ideas here for new things to try.