You will need a purebreed dog, preferably one with AKC registration to compete with, Although there is an option to apply for an ILP number for an unregistered dog it can be slow to get though all the red tape requirements. Also the registered dog needs to have the Juniors name on it's papers, or the Junior's parents or a close family member.
You will be expected to have proper show equipment on your dog, and to be able to control the dog at all times. Your dog will be expected to stand while a stranger, the Judge, goes over the dog all over, including looking at the teeth. How this is done will depend upon the breed of the dog you are showing, some are examined while standing on the floor, while others are set up on a table. You need to watch this, or go to Matches or Shows, or find someone knowledgeable to help you learn how to *stack* your dog. Basically this means to have the dog stand still in a pose with the front legs and feet straight with front legs directly under your dogs shoulders falling in a straight line down from the withers, and the rear legs also straight and directly under the back of the dog. The head and neck in a pleasing alert position and keeping you dogs attention with a toy or promise of a treat works well. Teaching your dog to be still and hold this position is very important.
The Judge will also expect you to move with your dog in such a way that you will show the dog moving at it's best gait so they can see the dog's movement and see that you can move your dog smoothly at a proper comfortable speed. Although in Juniors it is the handler that is actually being judged, you are being judged on how well you show your dog, so you need to practise a lot and be prepared to show in a smooth relaxed manner. The Judge also likes to be able to tell that you are aware of what is going on and paying attention to any hand signals or instructions you may be given at any time you are in the ring. A attitude of enjoying being in the ring and doing what you are doing helps a whole lot too. Smiles are always hard to beat!
There are many patterns that can be asked of you and your dog in the ring but the most common ones are a square which is around the ring, a triangle, a down and back, or sometimes an L, or a T. Click Here for illustrations of these patterns. The most important thing is to be sure and listen to the Judge and do what he asks you to do. Watch the other exhibitors for an idea of what you are expected to do, and if you do not understand the Judge you may ask to have the direction repeated, but only once, so be sure and pay attention..
Another important item in the showring is grooming, for both you and your dog, you must always show your dog in a clean well groomed condition. If it is a poodle please find someone to help you learn to properly groom it, learn how to keep the teeth clean, how to keep the feet clean and groomed, how to care for the coat of whatever breed you are showing. Be sure it is squeeky clean when it goes in the ring. You will need to also be clean and neatly groomed, Your hair combed and secured out of your face, your clothing clean and neat, This is not the place for loose sloppy clothing. Shirts properly tucked into neat slacks, or a neat clean, dress of proper length and with skirt adequate to run comfortably with. Hint, pockets can be very useful to hold a comb, dogtoy, kleenex and etc.
I hope this will be useful for any young people out there who are looking to learn and be able to bring their dog to a show and have fun and competition in the ring.
Another hint is to look around the area you are in and find a Kennel Club to join, they are almost always a great source of people willing (and eager) to help you learn.