Showmanship and Halter Classes, What can you tell me?

I'm wanting to start showing my QH filly in halter and/or showmanship classes. She is 11 months and will be a year on April 13th. What do I need to teach her and basically what do I need to know and do? I've never shown before so I need all the help I can get. She knows how to stand square, and she leads fairly well be we need work on her turns and getting her to trot when I ask. She's not been clipped before either so that's another thing we need to work on. Thanks in advance for your help.

Make sure she's at a decent weight with good amount of muscle. You don't need her to be fat, but not ribby.
It will really help you if she's ok with standing square for several minutes at a time. You want to get her squared before the judge looks you over and what you could do is just not worry about her squaring up until the judge starts heading down the line, that way she'll be more willing to stand for a shorter amount of time.
In halter you will want to wear a cowboy hat, long sleeve western shirt, jeans should be fine for the local level, and boots. Make sure your hair is tidy and you can tuck it into a bun under your hat or if it's short it should be ok left down.
In Halter the horse is being judged, not so much you.
Preparation starts months in advance with a good conditioning program to make sure there's enough muscle tone and you'll want to spend quite a bit of time daily just brushing to get a nice shiny coat. Clip the whiskers from the muzzle, any long hairs under the throat, around outside of ears/inside if you want, trim long fetlock hair, whiskers around eyes. On show day you want your horse to be as clean as possible. Get the mane tidied up and shortened, you may use hoof blackener or clear, depending on color of her hooves, I like using a small bit of baby oil on the muzzle to highlight it.
Getting her to walk at your shoulder without needing to be pulled along is great, same with trotting. I know the local classes here you usually just enter, walk towards the judge along the rail, and some judges ask that you halt, then trot along the rail, then line up in the middle facing the stands. Each judge may be different. A great idea is to go watch a show where you plan on showing later. It gives you an idea of how laid back it is, what to expect from judges, and your competition.
In Halter you'll want to move around when the judge is checking your horse to allow the judge to have a clear view. Don't cross behind the withers, stay by the head, but if the judge approaches the front left side, smoothly move to the horse's right side, keeping your toes pointed towards the horse's shoulder, left hand holding lead slack and right holding the lead closer to the halter. When the judge is at the rear of the horse, stay on the same side as the judge. If he's at the right rear, stay on the right front.
ALWAYS pay attention to where the Judge is, keep your eye on the Judge when he's judging your horse.

This is important; even in fun shows you can be dq'd for not remembering this:

In both these events you are there to PRESENT YOUR HORSE (and yourself)- to make it look special, unique and easy to handle and that you and your horse are a good team. Smile and remember to make your horse look as good and willfull as possible. Even in the event that your horse makes a mistake, don't show it and keep going and prove that even through that small mistake, your horse can keep going. Make sure you both look neat and tidy and well put together.

The biggest thing with young horses is when you change sides for the quarter system they stand still. Have a friend walk around her and pull her tail and what not so she gets the idea of standing still and having someone look at her. Some horses get weird out by it. Also teach how to trot off from a stop. SUPER big and very hard. You want her to trot off WITH you and not be dragging her behind you. In fact for showmanship your goal is to be able to do a pattern without a halter. You want to make it look like you have no halter and have no contact. Don't touch her in showmanship, halter it is ok.

Lead your mares nose to the judges left shoulder. The HORSE stay in line with the judge not you. Spot an arms length from the judge. When doing your quarters step elegantly.

Showmanship is big on presenting. Smile and stand up SUPER tall and look the judge in the eye be proud of your horse. Keep your attention on the judge at all times. Even if they run you over just look at the judge and act like "You put that in the pattern don’t you remember" I had a horse run me over in a class once and we won because of how I presented.

Like everyone else said you want her spotless and in good condition. A perfect fitted halter also helps.

This is a great pattern for a reference
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Were those quarters done right? I always mess that part up

She was actually pretty slow on all of them but that is the just of it. I try and move with the judge so once they step over the shoulder line I go with once they step over the hind line I go with.

Yea that's what I thought too. Thanks :)

Thanks for all the info, its been really helpful, we practiced her skills and I had my brother look her over, touch her everywhere, etc. He's hardly ever around her so she was a little nervous at first then just didn't care what he did.

You want her to stand square for a good length of time(I was once in a showmanship class that lasted over a 1/2 hour in the middle of summer somebody actually passed out), pivot on her hind end(90, 180, 270, and 360), back up, trot, walk, and you should learn to SHOW her(toes pointed towards her front toes, hands at 90 degree angle like you are holding a pie pan in front of you, etc)