As you may be aware, Freed of London has the honour of supplying many of the leading ballet companies throughout the world. Determining each dancer's individual needs relies on a vast amount of experience gained over a great many years. However, the first rules of fitting will always apply.

The starting point is your current walking shoe size (for US & Continental sizes, please refer to the chart below). Freed's lasts are fairly close to street sizes in length; it it usual to wear the same size or slightly smaller. It is most unusual for a dancer to wear Freed pointe shoes larger than her walking shoe size. However, it should be determined whether you intend to wear toe sponges or similar since this can actually alter the length by a half size.

Freed Pointe Shoes are available from stock in four widths, so it should therefore never be necessary to wear the wrong length to get the correct width. To check the width you should look at the bare foot flat on the floor and pointed forward. The fitting across the metatarsal can then be gauged. Both shoes must always be tried on. Initially, one should look at the "fit on the flat". When you are tanding with weight on the feet and knees bent, your foot will be at its largest proportion. The shoes should feel snug but not pinch, and the dancer should feel the block "cupping" the toes.

Check that the block contains the toe joints
Sole twisting away from the foot --- shoe is too narrow

You should be able to feel all three points of the foot's triangle on the floor, i.e. under the little toe joint, the big toe joint and the centre of the heel. At this stage the side seam is also checked for tension.

Place foot en pointe without transferring body weight. One can now establish the suitability of the shoe's width by checking whether the outer sole of the shoe remains flat against the pad of the dancer's heels. If the sole twists away from the foot, then this indicates that the shoe is too narrow. Check also that the block contains the toe joints. Both feet should be checked.

Next assist the dancer to go en pointe, it is important, particularly with a beginner, that help and encouragement is given. The dancer must not either releve or rise through the foot. Instead, taking both hands, one should assist the dancer to"climb" one foot, then the other foot, onto Pointe, whilst at always reminding the dancer to transfer their body weight forward onto their toes. Now one can check the heel for length. If the outer sole of the shoe extends beyond the pad of the person's heel, the shoe is too long.
When a dancer goes en Pointe they will draw her toes back slightly to give her feet additional support. This added to the fact that the foot will naturally curve in this position means that, en Pointe, the foot is shorter in length than when the dancer is standing flat. Quite naturally then, when en pointe the shoe will have a slight excess of satin in the heel area. This will be taken up when the dancer comes down.

If the sole extends beyond the heel, the shoe is too long.
From http://www.freedoflondon.com/cat/pointeshoefitting.php