I'm very late to the party and loads of excellent suggestions and tips have already been given. (e.g. I've done a few Pilates classes myself and I absolutely agree that this can be very helpful). Like many of the others have pointed out: there is no quick solution here, it takes time to 'find your new posture' and develop new habits.
First of all, thank you Angie for mentioning me specifically! It always makes me smile when someone on the forum compliments me on my posture!
I think I've always had relatively good posture, but it wasn't until I was eleven that I was made aware of how important it actually is. After a growth spurt I was sent to a specialist because my left leg was now suddenly 0,5 cm shorter than my right leg (it still is). I can't remember exactly what that doctor said, but he must have made quite the impression. I remember driving home with my Mum after the appointment and I started practicing sitting up straighter, with my shoulders down and head properly aligned right there and then. I kept at it for the following months, I was hyper aware of my posture during all that time. But after a while I stopped thinking about it, it had become natural. I guess I trained myself into better posture;-) (and that without anyone having to nag me about it at all, ever, that was a first, and a last;-)
However, having good posture doesn't mean one is immune to back/shoulder/neck pain unfortunately. After sitting in front of a computer for years on end, I have certainly developed my fair share of issues. Even if you are aware of your posture, I still often find myself all tensed up by the end of the day. Shoulders inching closer to my ears, hunched forward, neck and head 'sticking out' (and like Kari, being cold or stressed makes things worse).
I went looking for some exercises I could do at home, and stumbled across this dvd.
http://www.amazon.com/Posture-.....038;sr=8-2
She appears to be quite well-known in the States? The dvd looks a bit old-fashioned but her advice and suggestions are still very valuable I think.
I've never done the complete exercise set, and if you're pressed for time and can only do 3 things, then I'd suggest you try to do the following whenever you remember to:
- the 'arm wave': helps you stand up straighter, it relaxes your shoulders, repositions your arms and helps you find the correct alignment
- repositioning your head and 'tucking in' your chin
- the 'doorjamb' stretch, designed to stretch the muscles in your chest, very good for people who tend to hunch forward
Hope this helps a bit.