My simple advice, if it's good, score it well, if not, give it a 5 or 6, but let the cook know what you didn't like about it.
Person pet pieve of mine...if you go around afterward and a team asks, "Hey, eat any good food today"? Don't tell them "it was ok" or "not really", or "a little disappointing". That's last thing you want to hear after being up all night and busting your behind to put good entries in a box. Just lie if you have to! Otherwise, go buy a smoker, a pop tent and some meat and do it yourself!
Funny how these are the guys (or gals) with a full cooler of meat from their table to take home!
Ok, off the soapbox now, enjoy your experience, it will be fun and rewarding. The part above about helping to clean up would be a classy move...just be careful if you're ever by my tent, I just might take you up on it!