ballet exercises are very good. I have the NYC ballet workout video, and I find that the days I do it, I walk taller. Also, I think swimming is very good for elongating the spine.
In brief, when you stand you must keep your pelvis in a middle position, not sticking out your butt nor curving too much the other way. Your chin should be up, and you should think as if a rope was coming out the top of your head and pulling you up.
Von't know if I was clear, you can ask me if I confused you.
2) Roll your shoulders back. A good way to do this is to stand with your arms down, at your sides, and stick your thumbs out in the 'thumbs up' position (thumbs will be pointing straight ahead). When you roll your shoulders back your thumbs should be pointing out, away from the sides of your body. Your chest should feel "open". This always works for me if I catch myself hunching or slouching.
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"Don't be cool. Cool is conservative fear dressed in black. Don't limit yourself in this way." - Bruce Mau
In addition to ballet/dance exercises or classes, I would recommend yoga or Pilates. I always feel like I'm standing up straighter after I do the videos.
i agree on ballet and/or pilates. one thing i learned in pilates that is a quick trick to remember in your head--thinking about moving your head back so that it is in line with your neck and spine. as the day goes on, most of us get our heads going forward like turtles and they wind up being stuck fowrard from our necks.
sitting up straight in your chair with your stomach sucked in helps your posture. I think someone on here recommended that once. I always try to remember rolling my shoulders back ever since I watched the prince and me.