Call or email the show secretary and ask for a catalogue. Tell him/her that you have nev er shown before, and ask what all you need to do for that particular show.
Requirements vary by show, and some states have specific requirements as well. Typically, western states do not have any testing requirements, while those in the east do require NPIP or other testing and/or health certificates.
Make sure you are feeding your birds a GOOD feed, especially while they are growing feathers, and keep them in clean conditions that are conducive to keeping them clean and healthy, and will minimize any feather breakage. About a week before the show you will want to bathe your chicken; I personally prefer using a flea/tick shampoo with a residual effect. Makes sure any bugs they might have are killed, and will prevent them from picking up any at the show. Wrap in a towel to absorb moisture and a few mainutes later either blow dry the bird or put under a heat lamp. Blow dry in the direction feathers grow, unless a silkie, then blow dry against the way they grow. Keep bird in a warm place for at least 24 hours after it is dry. Clip toenails and beak as necessary for a well-groomed appearance, lightly rub oil into the comb and wattles.
Have fun!