Take with you the style guide so you can reference it. No judges judge without one near them. It is ok to reference it. Most judges talk about the beer as they judge quietly with the people they are paired with. it is ok if you do not pick up things the other judges are getting as we all perceive things differently. For example, an elephant has to fart in my face for me to pick up sulphur. meaning it needs to be fairly strong. A friend of mine can smell it a mile away. Toss acetaldahyde or Diacetyl in the smallest amounts my way and i can pick them out right away.
And above all, just relax. You are not doing oper heart surgery. It is supposed to be fun.