Train your dog at home to eat in different places. Indoors, outdoors, in different rooms and at different times of the day. (This will help so the dog will eat when you are away or when you take him to a show. )
Train your dog to a crate from the beginning so it will consider its crate its bed. That way you can take that crate into a motel, into the show site, set it out on the grass when it is a hot day and you are stopped at a restaurant with no problems.
Train your dog to go potty on a leash! Flexi leashes are great for this!
Train your dog to "settle" in the crate and in your vehicle. A raging noisy dog is NOT a good advertisement for your breed or yourself. Set up training situations if necessary and reward the dog for quiet behavior.
Always picture yourself in the "winner's circle" before you go in the ring!
Pick up your armband in plenty of time and check out where the restrooms are the minute you arrive!
Wear appropriate clothing and comfortable shoes.
Be sure your dog is groomed well. A bath and a brush are two key ingredients. Some people spend a fortune on dog show equipment and win nothing. Some people spend nothing (or hardly so) and win a lot. There is a difference in the amount of equipment you will need depending on the breed that you have. Poodles require a LOT more expertise and equipment to groom than German Shorthairs! A minimum for most people is a grooming table and a kit with brushes, wipe rags, etc.
PICK UP AFTER YOUR DOG! BRING ALONG PLASTIC BAGS AND USE THEM. People who don't do this are giving all dog shows and dog people a bad name and restricting our rights more and more at different motel chains.
If you have a young puppy or a dog that may be coming down with something and you're not sure, do not walk him in the public areas where other dogs are. Try to find an isolated area.
Be at the ring on time. (Always buy a catalog, it benefits the show giving club and it tells you where to go and when to be there!)
Get show photos if you take a win (blue ribbon or better) especially if the win is worth points. This is your record of achievement just in case the AKC or whatever show club is putting on the event mixes up the records or the records get lost.
Get in a good supply of peppermints (mints absorb the extra adrenalin smell from your own breath and will help to keep your dog calmer if you are nervous).
Watch your dog at all times around the ring, you may have a "good dog" but not everyone else does!
Keep your mouth closed and your eyes open.
Take along your vaccination records. All of them. The best idea is to always keep an extra copy in your vehicle.
Invest in a crate. For the larger breeds, a wire crate is best. Many of the larger breeds are coated and will get hot in an "airline type" of kennel, where a wire crate will give them more air..
Join your local Kennel Club! The people there can help you learn to show. And join your Breed Club if at all possible. These people will help you to learn to show and if you are a member, you will also know when the local shows are coming up!