First of all if you suck at D don't play D. Play the position that you are best at and most comfortable with. There are a lot of things that go into team play but some of the easiest to do are these...
-Shots on net, not just goals, are great for team play. However make sure you get the puck to the net because shots that get blocked or miss the net hurt your team play.
-Block shots as much as you can
-Clearing the puck from your own zone on a penalty kill
-This one is obvious but stear clear of taking penalties. That is a team play killer.
-If you are playing as a tough guy fighting at the right time and winning those fights helps
There are a lot of things you can do to up your team play. Just stay with it and stay patient, you'll get your card.