Ask your coaches what you should focus on. Seriously. They're the ones who know you and know what your strengths and weaknesses are - advice from strangers can be good to think about and test out in the long term, but for an imminent competition, you shouldn't try out something new.
For what it's worth, my coach will just tell me general things to keep in mind before a competition, like "don't rush" or "concentrate on making clean actions." (And he'll tell me to "have fun" too - which I really like

) The advice I like to give to nervous beginner fencers is "Relax and do what you know." A tournament is no time to be trying out the nifty new move you just learned last week - stick to what works well and that you're comfortable with.
Will your coach(es) be at the competition? If so, my advice would also be to *listen to them* when they give you advice between bouts or at the break. That sounds obvious, but when you're keyed up, it's very easy to "hear" but not actually parse the information. Try to mentally slow down enough to take in what your coach said - repeating the advice to make sure you got it is a good idea.
(Case in point. I was in the semifinals of a local tournament and fencing a DE against a woman with a killer parry 4. Guess where I kept attacking to? My coach, watching on the sidelines, is telling me "Change lines!" I keep doing it. "CHANGE LINES!" from the sidelines keeps getting louder. The audience knows I'm supposed to change lines. My opponent knows I'm supposed to change lines. Half my brain knows that I'm supposed to change lines. Apparently this is not the half that was in control of my tactics, however, because I keep attacking to the same #$@%! line and THEN realizing what I did. Not surprisingly, I lost the bout

Hehe. On the bright side, it was a useful learning experience for me (it often takes a disastrous DE bout to drive home a particular point... but hey, live and learn) and the next time I faced this fencer I won.)