If you're tall, you're in luck—for the most part: Ankle boots can make even the leggiest lass look stubby, so use a mirror. Dare to wear your ankle boots with bare legs and a mini dress.
If you're short: Pair your ankle boots with tights, leggings or pants that are the same color as the boot to create the longest line possible. Ankle boots have a tendency of visually chopping you off at the ankle, so be aware of this. Try topping your look with a fitted, cropped jacket to elongate your torso.
If you're plus size: Go for a monochromatic look on the bottom to slim and lengthen your silhouette. Pair with something like an a-line, 3/4-length-sleeve dress in a body skimming (not hugging) fabric that falls at or just above the knee.
Everyone: I'm stating the obvious here, but the higher the heel, the more height you'll get, hence the more likely you are to nail this look. Also, below-the-knee and long skirts don't seem to work with ankle boots no matter what your body type. Looks frumpy.