Just a suggestion from experience:
1. Let your table captain know you are new to judging - he will (or at least SHOULD) pay a bit more attention to you and what you are doing.
2. Talk with the other judges at your table before judging and get to know them.
3. Talk with the other judges between categories and LISTEN to what they say about each entry. You might not agree, but if their concensus is good and you think it was bad, then you might need to re-evaluate your criteria. Just saying...
4. MOST IMPORTANT - do your best to be fair and honest! The teams deserve nothing less!
5. HAVE FUN!!!
CMJ - KCBS
CBJ - MBN, NCBS, NCPC, NCBBQA
OBJ - BBQCritic.com
CTC - KCBS
Pitmaster and chef - "4 Lil' Pigs" Competition BBQ Team
Author of "A 'Q' Review"
Lang Hybrid Smoker, BDS, Holland "Epic"