First: buy good shoes. The engineering that forces the weight of your body onto different parts of a shoe make a huge difference in how long you can walk comfortably in them. They should be comfortable to stand in for at least 5 minutes before you buy them.
Practice on high tiptoes, so you get used to how the weight throws your legs and hips into a different alignment. Pull up on the front of your knees and lift your head toward the ceiling. Slouching while in heels will hurt a lot more than being upright.
Walk putting the whole shoe down at once, not heel then toe, which in very high heels is awkward and dangerous. Think of pressing forward through your toes and press from the back of your legs and butt when you walk, rather than pulling yourself forward with your hips and thighs. Push with your calves, not pull with the front of your thighs (which stresses your knees.)
at 5:33 PM on Jan. 8, 2011