Train the way you will compete.
The last several workouts before the meet have someone give you the commands you will be required to follow at the meet. For example, "Squat", and Press". If you haven't built the habit of following signals it is very easy to forget to when the excitement/stress of the meet hits.
Nearly every meet I see lifters lose an attempt because they haven't prepared themselves to lift with commands.
Attend the rules meeting that morning. Ask questions and get clarification on any rule you are unsure of. Odds are good that several other people in the group are wondering some of the same things you are but didn't want to ask
Talk to the judges if you miss a lift (in most feds) so you know for sure what you did that cost you a red light. You need to know the problem so it can be corrected before the next attempt.