Something with ankle support (ankle boots/bootshoe) if appropriate? [With trousers for example.]
Thicker heel = more stable?
Not too high? 3"-4" if you manage this with no discomfort usually.
Cushioned footbed.
Shoes that don't have any vices. Meaning when you put them on, they don't crush or pinch your foot or toes. Nor are they so loose your foot moves around in them.
For Look:
The highest pair you can afford.
Oh, and get plenty of practice before the big day?
The most important thing is practice. If you don't choose a boot, go for something with an ankle strap to help ensure the shoe stays securely on your foot.
Good luck and enjoy!