How do you become a good team mate ?
What skills are needed for cooperation ?

This applies to Warlight and other type of games. I am a *bad* team mate. :(

be willing to listen to suggestions. if i know a teammate is much better than me, i will ask for advice and follow close instructions if they are given to me. if i think i know a good move to make i will say it, and if someone disagrees i will work with them to figure out the best plan of action. communication is really important. so is having the attitude that you don't want to be the guy that loses the game for your team. play your best game and don't give up on it even if you are personally getting beat.

number one though, don't get booted. you are instantly the worst teammate when you get booted.

Play games in team with your own alts.

It might seem paradoxical but it helps you understand what's the best move for the team's sake (and not for the single player's sake) and it forces you to understand your mistakes and improve, since you have no teammates to put the blame on.

Be cooperative. You can thank me later.

play EU 3v3 with someone who's good at it