DD has been on pointe for 10 years and is currently a soloist in one local ballet company and a contributing artist in the other; we have been through more than our share of pointe shoes! Previous posters have made lots of good points (no pun) to keep in mind.
When I fit a shoe, any kid who tells me it feels good is lying! Pointe shoes should fit like a glove. Unfortunately for the paying parents, they can't be fitted with a little space for growth; the dancer will slide in the shoe and will get hurt. Pointe shoes should feel a little too tight when standing, as the foot will change shape slightly when on pointe and the shoe will fit better. Heel fit is as important as anything else; not only does it need to fit snugly, but by looking at how the heel fits, you can tell if the shoe is twisting. Your dancer's shoe should fit snugly as she stands on two feet, with her toes should be flat on the floor, not pointed, curled, or scrunched up.
As far as shoe accessories:
Toe Pads: Check with the teacher and see what she allows for toe pads. Many of the thicker gel pads keep the dancer from being able to feel the floor; NOT a good situation! Also, many of the girls find that the thicker gel pads constrict blood flow and make their toes numb- another bad situation. DD likes the Gellows, which are fabric on one side and a thin gel lining on the other. Toe pads need to be stored someplace where they will dry. DD keeps hers in a mesh bag. IDEALLY, the only thing inside a dancer's shoe should be her foot; keep the padding to a minimum for best control of the shoe!
Ribbons- I recommend Flexors. These have a piece of elastic that you align across the dancer's Achilles tendon (align first, then pin in place). The elastic allows the ribbon to flex slightly and keeps some of the pressure off the tendon, to help avoid tendinitis. Other companies make elasticized ribbon, but you don't want the ribbons to cling tightly; you want them to stretch. It's also really nice to have soft, shiny pink ribbon!
Elastic- most teachers require elastic to keep the heel of the shoe in place. DD likes Gaynor Minden elastic the best; it's soft and stretchy, but strong. Check with the teacher to see what she likes- or ask the older dancers at your studio. The teacher should show your dancer where to place the elastic; although there's a "traditional" placement, it's really more important to find where your dancer's shoe gaps or slips and place the elastic accordingly.
Spacers- Most dancers wear a gel spacer between their big and first little toe. This helps keep the big toe aligned and helps prevent bunions (which are an occupational hazard). You can order these, but DD buys hers at the local pharmacy (Rite Aid) in the foot care aisle. IF your dancer has a little toe that naturally tucks under her other toes, you can buy skinny little spacers to keep that baby toe aligned.
Toe Caps- Most dancers should not be wearing toe caps. It's just another layer of stuff keeping the dancer from feeling the floor. An exception to this is the dancer whose second toe is longer than her big toe. These dancers sometimes need a cap on their big to to even out the length.
Tape- Many dancers tape their toes when they feel chafing begin. Blisters and pointe shoes are an ugly combination! Different dancers prefer different types of tape. DD used to use the clear plastic, slightly stretchy first aid tape (the kind that seems to have perforations and tears evenly). However, during a summer with the Rockettes she learned that they recommend masking tape. It works well and is the cheapest alternative. That's what she now uses most often.
Care of pointe shoes: The boxes (hard front part of the shoe) of the vast majority of pointe shoes are made from layers of muslin or paper and paste. Since feet sweat, point shoe boxes soften up when they get damp. While this is good to some extent as it allows the shoe to mold to the foot, it also weakens the box and shortens the life of the shoe. Pointe shoes need to be dried between wearings to protect their integrity. This means DON"T keep them in anything plastic. Ideally they should come out of the dance bag each night (DD leaves them on top of her dance bag, so she doesn't forget to take them the next day). This is important, when you consider that pointe shoes cost in the neighborhood of $100 a pair, and many will be dead within 6 hours of dance time! Also, anything with gel (toe pads, spacers, etc) should not be kept in plastic bags either (I know lots of kids who keep them is ziplock sandwich bags, but this is a BIG no-no!). DD has a mesh bag (delicates laundry bag from Dollar Tree) that she keeps all toe paraphernalia in.
BUYING- Pointe shoes are expensive. No two ways around it, and they need to be replaced when they start to break down, wear through the platform (this isn't' when the satin wears off
this is when they wear down into the padding so the raw material of the box shows through), the shank breaks, or the kid's foot grows or changes. If the shoe is the wrong size or your kid's foot grows/changes, she should have a new fitting. Once her foot has stabilized, if you choose to order pointe shoes online (that's how DD gets hers), DON"T sew on elastic or ribbon until the teacher approves the shoe if it's a new style or size. Pointe shoes can be returned, but not if you've sewn anything on them. (One year, after DD came back from an injury, she needed a completely different shoe, but our closest pointe shoe store was a 3 hour drive away; I had no fewer than 9 pairs of shoes in my dining room for her to try on. She ended up finding ONE pair that would work temporarily until we had the opportunity to go for a fitting- all the others went back, and yes, I was out the cost of shipping!)
Pointe shoes are an investment, but please don't cheap out. Think about what you are asking your dancer to DO in these shoes. Dancing on pointe is NOT a natural use of your kid's feet, and she is going to need these feet a LOT longer for far more things than she's going to be dancing on pointe. It gets expensive if your daughter is serious about performing. DD's feet are 2 different sizes, so she has to buy two pairs at a time. Some companies are notoriously behind in stock; girls will order 6 pairs of Russian Pointes at a time when their style is back in stock. It is what it is; I am just glad it doesn't cost as much as outfitting a hockey player, even if the dance bag smells as bad or worse than the sports bag!
. I am wondering how these things are supposed to fit. I realize they are not going to be the most comfortable shoes, they aren't made to be. The ladies at the store who fit her seemed more concerned with how the back heel fit into the shoe when she did a releve than how they felt at the toe area. When she walks they are tight and pinch her feet, when she is on pointe they feel better. I know they will break in, but she was much less enthused when she got home and tried them on here. She will have her dance teacher look at the fit at the studio, of course. I am curious if this is par for the course with them feeling not so great, even if the store says they are fit properly? I hate to spend so much for shoes (anyone who knows me knows I always buy them online to try and save a few bucks 
) and have them be totally wrong after we sew the ribbons and elastic on them. I guess I am just a little nervous because of the expense. I cringe at how tight the dance teacher wants the girls' shoes to be, I am trying to get over that!
. My daughter is just starting out, her teacher is not one that is going to have them on their toes for more than a few minutes a week. I am not worried that this is going to be an instant pressure on her and her growing body. The students had to show the instructor how good their ankle strength appeared to be before she would approve them for moving to pointe. We will see how this goes 
.
