A convention card describes the conventions agreed upon by players when playing as partners. Players must have in their possession a copy of their convention card completed at the beginning of each bridge session. Blank convention cards are available at the clubs where you play. On the back of the card, you can write down the contracts and results of each board you play throughout the session.
The ACBL has published a series of steps, each describing how to read and complete a convention card. The articles are based on the Conventional Wisdom column from the Bridge Bulletin.