limey

almostaugust had some good advice. Positioning and anticipation is critical when you don't have the ball and these areas are different depending on what position you play. An important aspect of team play is knowing where your players are most of the time and especially your immediate players. A basic rule is always know where you are going to pass the ball before you get the ball. That way you spend less time thinking with the ball at your feet and you can react quicker under pressure.
Here are some REALLY basic tips for team play depending on your position;
Defender:
Make sure you are always covering your man (unless you are playing zone coverage) and you can beat him to the ball if it goes sailing over both of your heads towards your goal. If you are playing the offside trap make sure that you keep up with your line of defence. Make sure that if you push forward there is someone to fill in and cover your position. Don't commit unless you are sure you will win the ball and try to stand on your feet as much as possible - alot of defenders slide around making great tackles but they are sitting on their butts and cannot recover quickly.
Midfield:
Here you should get specific intructions from your coach depending on your teams' formation. Make sure that you don't get caught up field or left back. Try to support all areas of the team and don't hang on to the ball too long. Here, your main goal is distribution in attack and hussle in defence. Try not to do everything and be everything.
Strikers:
This is all about timing your runs, where to run and when to use your indiviual skills. Strikers usually have close ball control and explosive speed over short distances. Balance, speed and accuracy are essential here.

This is really general and I'm sure that everyone has their own opinion on each but if you have somehting more specific I will gladly help.