1. Pretend / fake it
Say things to yourself like "I am nature's greatest miracle!". This is from a Simpsons episode but I find it makes me feel good to say it. Wear nice freshly cleaned clothes when you are in social situations. Spend a lot of money to get a decent hair cut and maintain it by going every month. This will make you look more confident and people will respond to you like you have a dominant personality (an alpha). You are not, but they will treat you like one.<p>2. BE confident. Clearly and politely state what you want. Be prepared for rejection -- in fact seek rejection out to condition you to not care. Learn to call people by their name. It is music to their ears and they will enjoy your company more.<p>3. Do something that you feel is risky (but safe), like sky diving or entering a boxing tournament. Hopefully you will survive and you can draw strength in the future from this experience.<p>One of the "secrets" of life is we can pretend to be anything, and the longer we pretend, the more we actually change. Society will reflect back to you what you put out. Look at people and smile, they will start saying "hi" in return.
This TED talk may be useful. (piggybacking on lifeguard's ideas):
<a href="http://www.ted.com/talks/amy_cuddy_your_body_language_shapes_who_you_are.html" rel="nofollow">http://www.ted.com/talks/amy_cuddy_your_body_language_shapes...</a>
Try Rejection Therapy
<a href="http://en.wikipedia.org/wiki/Rejection_Therapy" rel="nofollow">http://en.wikipedia.org/wiki/Rejection_Therapy</a><p>I find it the most difficult but at the same time the most efficient solution for low esteem issue.
Low self esteem is often rooted in a disconnect between perceived ability and actual ability. Seeking some kind of objective measure which gives a clearer idea of where you really stand can be very helpful for some people.