Read the WSB, pay attention to the round count. Walk the stage and count the targets and make sure these numbers match. If not, you forgot one.
After that set your plan, and review it 100 times until it's your time to shoot. You should be able to close your eyes and run through the entire stage in your head at that point. Most new people don't walk the stages enough. Maybe they think they are in the way of other people or something, I dunno, but I see it all the time. The worst shooters at the match will walk a stage once, think "I'm good", then go stink it up....I wonder why.