well there is no reason to be neverous at a comp. i was at my first comps, even if i couldnt do shit, but no more, regardless of magnitude.
But as for stuff to do... depends on the format. If you get like two runs, best run counts, then its better to just throw a nice run that you can stick, and save the bigger stuff for another day. Trying new shit at a comp can be good, it can also be bad. If you get a lot of practice in, and its more like jam format, and you feel confident in your skiing, then it doesnt really hurt to try some new things (within reason, dont want to get hurt). But really, its better to go into a comp with some stuff solid, rather than trying it then.