What are you entered in? There are open shows as well and youth, 4-H or showmanship.
Open shows are open to anyone who has a purebred rabbit. These shows mostly follow ARBA guidelines and breed standards. The rabbits much be purebred and intact to show. In these shows, you don't do much. You take your rabbit up to the judges table and put it in one of the coops there. The judge will then judge and place each rabbit. Once the judging for that breed or class is done, you take your rabbit back to it's cage. If you won the breed, your rabbit goes on to compete for best in show.
Youth and 4-H shows are run pretty much the same as open but it is only open to youth (under 18) or those in 4-H. Rabbits are not disqualified where they would be in an open show. The rules and standards are the same as an open show.
Showmanship is a bit different. This is you presenting your rabbit to the judge. This is usually done for 4-H. The rabbit does not matter as much as how you present it. You could have a rabbit that might come in last in the open or youth show, but you could do first in showmanship as it is based on you rather than your rabbit. Since you don't seem to know what you are doing, don't enter this as it does take some practise to know what you are doing and to get it right.
Some fair shows are run a bit differently. Around here there tend to not be enough entries to do separate breeds. Instead they do Fancy, pet and heavy rabbits in both buck and doe, so 6 classes. You just enter your rabbit in the right class. Breeds are still judged on ARBA standards expect for mixed breeds.
It is important for you to make sure your rabbit it ready to show. Clip the nails a couple days before you go (so they aren't sharp or rough and any bleeding has stopped). It is also good to brush him out before you go, but be careful if he is moulting as you can over groom and he would look funny. At the show, brush him out again and just make sure he looks good. Any stains on the feet should also be taken care of before you go.
Ask people when you get there. Most are helpful and willing to give you some tips if needed. Some are busy, so try to avoid asking as they go to the table or are watching the judging. Someone who has your breed can also be helpful as they would be showing when you are.