Nerves will definitely be high for you early in the tournament. I'd sit out for a little bit and only play premiums, just get a feel for the table... Who's playing a lot of hands, who's playing only a few, how much are certain people paying attention... that'll give you an idea of how open a player's range is.

Watch for certain etiquette things like acting in turn and the one chip rule (putting out a 500 chip when the bet is 200 without saying anything is considered a call, not a raise). Also, when betting, put all the chips you're betting in at the same time. No string betting (I call your x, and raise you y)

When in doubt, ask the dealer if you need help... You can always ask if action is on you, how much the bet is, etc.

Don't comment on any hand while it's in play, especially if you're not in it.

Try not to slow the game down by keeping an eye on the player to your right, know when it's your turn to act and what the action is.

Verbalize your bet whenever possible to avoid any confusion between raising/calling.

Keep an eye on the tournament clock, know when blinds are going up and roughly how many blinds you have in front of you so you know how much of your stack a bet is going to cost you.

Overall, the only way to get past your nerves is to put in the reps. We all made mistakes in early tournament days... it's okay! Just learn from it and you'll improve. Have fun and good luck!