What are some good ways to improve self esteem?

I think all of the answers that will actually bear fruit long-term can be distilled to this: acquire capabilities, and become noticeably skilled at at least a couple of them. Be capable of doing [i]something[/i] which will evoke admiration in others.

After that, the best advice is to just wean your self-image off of dependence on others' perceptions, but that is [i]much[/i] easier to do if you have the confidence that comes with being skilled.