KS has some great advice. Also, there are some really basic things that you need to know. One is that your chickens must have leg bands. If she is already banded, then that there you are. If not, then banding is easy and you can get bands at farm supply store or order on the internet. The chickens can have wing bands as well, but they have to have leg bands regardless if they have wing bands.
Also, I bathed my birds a few days before and kept them clean. I had to bathe a few days before since I showed around 20-25 birds at a crack. With one bird, especaily a feather footed breed you can bathe the day before and blow dry out. Keep her in a clean area after the bath. This is where you till trim spurs, and toe nails to shape. Then on show day, make sure you have spot cleaning equipment with you. Clean rags and a spray bottle with a little soapy water mixture to spot clean stubborn dirt/poop without getting her wet again. I also used a product called "Pink"-in a spray can. You can get it at a drug store in the hair section. I used it to dust/shine up the feathers and add a little moisture to them. Just spray alittle on a clean dry towel and rub the chicken all over. Also you can use a product called VetRx. It is an herbal oil that you can dap just a tiny (a little goes a long way) amount on the chickens comb, and waddles to bring out the red.
For your first show, you might just want to keep it simple and bathe your chicken and then once your at the show, look around and observe people and products that they use and get advise from them. Chicken show people are super nice and love to help "newbies". There is usually a person at the show who sells show products and equipment. This is a good place to get some of the stuff you will need for the next show.
Another important bit of advice can be obvious, but it happened to me at my first show because I didn't know any better at that time so I will impart it to you! You can't show a bird with clipped wings/feathers. I had clipped my RIR's wings because I didn't want them flying about. Well, I thought it would be fun to show my two pet chickens and I got DQ'd. I had ton of fun anyway and I learned a lot that first show. Along the lines here as far as I know, they also cannot not have toe punches. (Used for identification at hatcheries shipping more the one breed in a box-most customers have to request this though when orderig). Having toe puches will DQ a bird.
Another helpfull hint is to take extra carriers/chicken transport cages with you. You will want to bring back chickens from your show. You might have an iron will and wont, but there will be alot of different breeds at the show and if you stay with bantam brahmas, then hopefully you will hook up with some breeders who will be culling good stock. Poultry shows are a great place to network for good show and breeding stock plus you will have some of the best breeders of specific breeds in one place to pick their brains and get hands on help with what to look for in your chosen breed. Also, some shows will have a sale barn or a poultry swap.
You will need to find out if the show is a pre-entry only show or if you can enter the show day. Most shows are pre-entry only so you have to make sure you get your entry form in the time frame that you are given. Once you are at the show grounds, you then go to the entry table/area to "coop in", this is the time that is posted to bring your birds to place in the cages/coops. ( It's usually an hour or two before the judging starts.) Cooping in consists of getting your coop number so you know where to place your bird. Once you've cooped in, "fluffed" and spot cleaned your bird, make sure you give her some water and a little bit of food. Usually the club putting on the show provides these. After that your done with your tasks. Now, you just have fun and meet peope and birds! You can keep tabs on your bird through out the day, but keep an eye on where the judge is. It is common show etiquette/courtesy not to be in the same row that the judge is judging in. At our shows, we would block off the row the judge was judging in. Once the judge is done judging with the row, then you can look at the placings.
Once the judging is all done and the champions are placed, then you can coop-out. That means going to the entry booth and picking up any ribbions or trophies you've won and collecting your bird. Some shows are two days and coop outs are the second day. If your not sure about when coop out is, don't hesitate to ask the entry booth people. They can give you all the details on when and how they will coop out.
The show is also the place where you will be signing up for the APA (if you arent already a member) and the local breed club and/ or chicken clubs as well, again if you arent already a member.
So, remember to pack your show kit with extra pens, a pad of paper so you can get names and numbers of breeders, organizations and the like.
Also, make sure you have cash for food, bird purchases, equipment, and raffle tickets.
My show kit (basic version) included bottled watter and a some of my own chicken feed and a container of mealworms. I also included water and snacks for me. I had a basic First Aid kit both for me and my birds, rags, my Pink, my soapy spray bottle, more rags, a small bag of clean shavings to line any new carriers I bought, especially when they had new birds in them! An extra egg carton or two for any eggs that were laid, extra leg bands, folding chairs, pens, pad of papper, and an item for the raffle table.
The most important thing is HAVE FUN!!!! Chicken showing is the best! So have fun and learn and try not to bring "too" many birds home!! lol