Being a team player means listening to everyone on your team. You need to be able to efficiently get your point across and, at the same time, listen effectively to make sure your teammate has gotten their point across.
You need to be a reliable person. If the team entrusts you to do a task then you should do that task. If you con't be dependable you bring down the whole group.
The best way to succeed is to be honest with your team. If you can't do a task or you don't like the idea then you need to say something. That way you can see to it that your team is successful and can run quickly and efficiently.
Your teammates are people too; treat them like it. If you are upset then work it out without lashing out at a group member and if another group member is upset just to work it out using kind words so you can fix the problem.
Keeping a positive attitude will make a group experience more fun. Having someone who is negative and has a poor attitude with bring the whole groups mood down.