Here are some great tips on how to maintain proper posture when wearing your heels. I recommend always starting on the head and working your way down. Head should always be in line with the spine. Try and kick the chin up and level with the ground. You never want to be looking down to the floor on where your feet are walking. Shoulders should always be back and down, which will not only make you look stronger and more confident, it will make you look thinner.
Abdominals should be engaged, which will protect the lower back. A lot of women who wear heels complain of low back pain so by keeping the abdominals engaged, you're not only maintaining proper posture but you are protecting your lower back.
Knees, you should always have a slight bend in the knees. Try never to lock them out. Some of the most common mistakes I see in stiletto posture has to do with the head alignment. Head is looking down, shoulders are slumped forward, pelvis is shifted forward, which is going to cause neck pain, shoulder pain and back pain. I also see women turning their feet out.
Remember that proper posture is the foundation to looking strong, confident in your heels and having a graceful stiletto walk.