Standing

Keep your head high, chin in, shoulder blades slightly "inched" together. Think of angel wings or as my osteoporois Yoga instructor suggests: stand tall and lead with your heart.
Maintain the natural arch of your lower back as you flatten your abdomen by gently pulling it in. (Check the exercise posts on pulling navel in towards spine)
Point your feet straight ahead with your knees facing forward. (Feet and body should always go in the same direction)
While standing in one place for more than a few minutes, put one foot up on a stool. Switch to the other foot every so often. You'll find this much less tiring for your back and legs.
Brushing teeth, place one hand on sink.