Fit is everything. I don't care what your body type is like: If you're not wearing clothes that fit you, you can't have style.
A lot of women don't realize that even a small heel helps you throw your shoulders back and keep your chest up; it really does make a difference in the way you present yourself. It changes your posture and makes you look more confident.
Less is more. I truly believe in buying a few pieces with better construction.
If you deny the reality of your body or your life, you'll never be able to dress any of it well - even the parts you love. You have to see it all to work with any of it.