In texas holdem poker the term Fish is used to describe the weakest and least experienced player at the table. You never ever want to be the fish. It is commonly said that if you look around the table and you can not see the fish you are in his seat.
The best way to avoid being the fish is to look like you belong. This means do not walk in the room and look overly excited. It has to seem like you have been there before and you know what you are...