Dave Munger looks at a study on how people build reputations:

It turns out that your reputation for cooperativeness is only affected by your behavior if you're already popular. If you're not popular, it appears that no one takes notice of your behavior, so it has no impact on your reputation. People with lots of social connections can build a good reputation -- or a bad one -- with much more ease than people with few social connections...

So it may be that the reason I never became popular in high school was that I was going about it backwards. Instead of trying to acquire a reputation first and get friends later, I needed to get the friends first, then work on my reputation. But how do you get friends if you don't have a reputation -- good or bad? That, unfortunately, is what makes high school such an awkward time for so many of us.