From working retail in the juniors department, I've learned that most jeans are made for the "average" girl. This means according to sizing charts, there is a ten inch difference between the waist and hips. If you measure the smallest part of your waist and the widest part of your hips (which will go over your butt) this will give you an idea of where you fall.
Because the difference for me is about 12-13 inches, jeans never fit! If they fit my butt and thighs, they are always way too tight in the waist. I know many people who have small hips have the opposite problem, where if it fits in the legs and butt, it is too loose in the waist and they have to wear a belt.
I think finding that perfect pair involves lots of trying on brand after brand, size after size, since even brands, styles, and sizes vary tremendously.