This was a big realization for me personally:

If you are trying to get someone to like you, you should strive to maintain a friendly, positive interaction with that person in which he or she feels comfortable and happy on a moment-by-moment basis. You should not try to directly alter that person's opinion of you, in the sense that if you are operating on a principle of "I will show this person that I am smart, and he will like me", "I will show this person I am cool, and she will like me," or even "I will show this person that I am nice, and he will like me", you are pursuing a strategy that can be ineffective and possibly lead people to see you as self-centered. This might be what people say when they mean "be yourself" or "don't worry about what other people think of you".

Also, Succeed Socially is a good resource.