My approach to the 3 attempts that has worked well for me so far:
1st lift - ~90-92% of my current 1RM (this is to have a successful first lift and work out the nerves)
2nd lift - Very small increase over my current PR
3rd lift - Further increase (if 2nd attempt was made or if you feel like you can anyway), or repeat the 2nd lift if it was missed
If you haven't been training the two lifts together in the same workout, I'd start doing that at least once a week. It's amazing how fatigued you can get in a meet when your training only has you doing one lift a session.
Know that nearly everyone there wants you to lift well. Try not to be self-conscious, just go up there and do your thing.
A little extra coffee/caffeine an hour before the meet starts can be very helpful.