The best and easiest way to break into the show world is to find a mentor. This is often the breeder of your puppy. They have been there, done that, and can help to show you the ropes.
If for some reason you can't find a mentor (or you have a fiercely independent streak and want to "go it alone"), you'll need to start long before the puppy hits the six month mark.
First, of course, the puppy must have a Full AKC Registration to be able to compete in AKC conformation shows. The puppy must also be intact (not spayed or neutered) for the entire time you are showing it in conformation. (This relates to the original purpose of conformation shows, which was to evaluate breeding stock.)
It is never too early to start puppy training! Sessions should be short - just a few minutes at a time - and fun!! You should start out working on stacking and leash breaking. There are several great articles on training puppies for the show ring:
Spending time stacking the puppy every day will also get her used to being handled and groomed. Socialization is important, too, and she should experience as many new sights and sounds and people and dogs as possible. You should also practice grooming her, again short sessions, working on her nails, trimming ears and whiskers and flanks. This practice is for you, too! If you're not sure how to groom a Boxer for the show ring, talk with a breeder or handler (or, if one isn't available, get the book "The World of the Boxer" by Rick Tomita - it has a great section on grooming.)
Once your puppy is a bit older, it's time to start practicing. Many obedience clubs offer drop-in conformation classes, which will give you a feel for what happens in the ring, and will get your puppy used to having to pay attention to you while being around other dogs and people (not always easy for a Boxer puppy!).
There are also Matches, which are like practice shows without any points awarded. They can be Boxer only, offered by a Boxer club, or all-breed offered by a kennel club. Most matches allow puppies of young ages to participate - usually four months, although some allow as young as two months. Matches are typically casual affairs, and entries are usually accepted the day of the match.
Once you've been to a couple of matches, you should think about whether you want to show your puppy yourself, or you want to hand her over to a professional handler. There are benefits to both. Professional handlers are more experienced, and truly know how to bring out the best in a dog. They do this for a living, so they don't worry about having to "find time" to work with the dogs or take time off work to go to shows. Showing her yourself (owner-handled) takes a lot of hard work, patience, and sometimes a thick skin - but finishing a Champion owner-handled is a special kind of accomplishment. It is a personal choice, and not one you have to make right away. You can show your puppy in her puppy classes while you're deciding, since the judges are much more forgiving of handler - and puppy - errors at that young of an age.
OK - so now you've practiced with your puppy, you've decided to show her yourself, you've been to classes and a couple of matches (and even won your class! Who cares if you were the only one in it - a blue ribbon is a blue ribbon!). Your puppy is turning six months old in a few weeks, and you're ready for the "real thing." Now what?
The first thing to do is to find out when and where the shows are. You can check with the show superintendent - most of them have websites, and there is a complete listing here: http://www.akc.org/events/static/index.cfm - but you'll have to ask around to find out which one(s) usually handles the shows in your area. Another way to find out about shows is to subscribe to the AKC Gazette, which is a monthly publication. The Gazette is filled with great information, but more importantly it comes with the AKC Events Calendar, which lists all upcoming shows for the next four months, in calendar order by state, including judges names, closing dates and superintendents. Information on a subscription to the Gazette is here: http://www.akc.org/pubs/index.cfm
Once you enter a dog show through a superintendent, you get put on that superintendent's mailing list, and you receive "premium lists" of upcoming events in your area. A premium list includes show information, judges, classes offered, prizes, and entry blanks. It will also tell you what the entry fees are (typically $20 - $30, depending on your area and the show. Puppy classes and Bred-by-Exhibitor classes often have a lower entry fee) and when entries close ("closing" is the latest time that entries will be accepted, usually about 3 weeks before the show).
Once you've submitted your entries, it's time to think about what you're going to need for your first dog show. It's best to start shopping now, so you don't run into a crisis at the last minute!
COLLARS AND LEADS
First, you need a show collar and lead for your puppy. A show collar for a Boxer is a slip collar, or choke, made of nylon, leather, or chain (serpentine or hexagonal only - no obedience chokers here!). For a puppy, nylon is the best option. It's the least expensive, since you'll be replacing it often as she grows, and is the gentlest on her neck. The collar is placed high on the neck, right behind her ears, and should only have an inch or two of extra collar when it is fit snugly. Appropriate colors for nylon are white, black, or brown. The idea is to make the collar almost invisible, not to draw attention to it - hot pink is not a good idea, no matter how cute it looks on your puppy!
Show leads are made of nylon or leather. It should match your collar (unless you're using a chain, in which case it should be neutral). There are two types of leads, regular leads (which have a clip at the end to connect to the collar) and loop leads (which loop around one ring of the collar). Loop leads eliminate the possibility that while you're holding the lead, you'll accidentally unclip it from the collar; clip leads are easier to interchange with different collars.
There are also all-in-one leads of nylon or leather, and martingales. The all-in-one leads are not generally used in the Boxer ring, and martingales are for toy dogs.
You may use the collar and lead you've been training with, as long as they are clean and in good condition. Nylon show collars and leads can be placed in a pillowcase which is then tied in a knot to close it, and washed in the washing machine.
You will also need bait for your puppy. Typically liver; however you can use whatever works for your dog that is easy to break into small pieces and store in your pocket. (Steak is a popular alternative for people who can't stomach liver!) Some dogs, Boxers especially, get *really* charged up about liver or steak, so you may need to find something a little less exciting.
Some dogs bait better with a favorite toy, typically a "squeaky" toy. If this is small enough to fit in your pocket, you may use it instead of food - but DO NOT squeak when the judge is examining someone else's dog. It distracts most dogs, and will get you at minimum dirty looks and sometimes a fight. Also, don't squeak outside of the ring when there are dogs in the ring. Usually just showing the dog the toy will get his attention. Watch professional handlers who use squeakers, and emulate them. Most dog supply vendors sell pocket-sized squeaker toys.
You will need to think about how you are going to dress. AKC conformation shows are much more business-like than matches, and you will need to dress appropriately. For men, this means dress pants, jacket and tie. For women, a dress or skirt, or skirted suit. Pantsuits are becoming more acceptable, but some older judges are turned off by them. Shoes are of the utmost importance - they should be comfortable and sensible, and allow you to move freely around the ring. High heels do not belong in the show ring! Your skirt should be long enough to accommodate you bending and kneeling by your dog without giving the spectators at ringside a show! Also, low-cut blouses, while some judges may appreciate the view, are not appropriate.
Basically, what the judge is wearing is the minimum that you should wear. If it is very hot, the judge may remove his jacket - then and only then is it acceptable for you to remove yours. (Don't do this if you're already in the ring, though!)
Women should have their nails neatly polished or buffed. Hair should be styled in such a way as to not fall into your face - or your dogs' - when you are bending over the dog to stack it. Jewelry should be simple, classic, and kept to a minimum, and if you wear bracelets only wear one so that nothing makes noise as you are moving your dog.
Remove any loose change or keys from your pockets before you go into the ring. The attention should be on the dog, not on you or your noisy attire!
Your clothing color should contrast with your dog - you don't want to wear a tan skirt with a light fawn dog - the dog will blend right in with your legs! Subtle patterns are fine, but again the goal is to highlight your dog, not distract from her.
Whether you're going to a local show that you'll drive to and from each day, or to a farther away show where you'll be staying over will determine what kind of "stuff" you need to bring. If you're not going to be going home, you'll need to bring your puppy's food (and bowls), grooming equipment, potty bags, crate, ex-pen if you have one - plus your own grooming equipment and change of clothes.
Regardless of where the show is, there are certain things you will need to take, including small towels for ringside (Boxer + liver = mess!), dog's registration and health records, a spray bottle of water for ringside.
About a week before the show, you will get your entries and the judging program in the mail. Entries are the slips of paper that must accompany the dog to the show - they prove that the dog is entered (at many shows unentered dogs are not permitted) and usually if you have one you don't have to pay an admission fee at the show. The judging program tells you what time Boxers show (usually early in the morning), what ring they are in, and how many Boxers are entered. For example, a judging program that shows 50 Boxers entered, and then lists 25-20-(3-2), means that there are 25 class dogs, 20 class bitches, 3 Champion dogs and 2 Champion bitches entered. The judging program will also give you directions to the show, and any rules of the show-giving club or the show site (these are often included in the premium list, as well).
The night before the show, you want to give your puppy a bath and groom her (this is where all that training and handling comes in). Grind or cut her nails back, clip her whiskers, and trim any scraggly hairs. It seems like a small thing, but it can really clean up her outline. Then, try to get a good night's sleep!