good luck dude. my advise is not to be nervous AT ALL, easier said than done, but if u can manage to be relaxed, chances are ur opponent will be more nervous than you and thus u have a little advantage there
if ur take downs suck, dont try them! i learned that the hard way. check out my tourney vids on my youtube, the link is in my signature for the post. that was my second tournament but it was white belt level and you get to see the kind of shit people try at competitions and what u may expect.
Dont expose ur legs because that will tempt them for single leg take downs.
Good luck man! post ur vids after