I hope this doesn't come off as sexist or anything like that, but I've been really working on my confidence for the last year. I'm a bit of an introvert, and feel more comfortable around computers and talking through text messages than I usually did being around people. It actually made me a little bit paranoid in thinking about how others perceived me.
As a result, I began watching a bunch of "pickup artist" videos on YouTube. While I completely disagree with their goals, I admire the confidence of many of the people who do that. I think my favorite was this video on YouTube: http://youtu.be/1mRM1VwUiYA It got me thinking, and so I made the goal that I would get a girl's number every day for a week last March.
That week I really worked to make the goal happen. Walking around my college campus, I went out of my way to walk next to girls I thought were attractive, and sat next to them in our food court for lunch, and in the library. Originally I had thought that they would all turn me down or at least seem a bit annoyed about it, but by the end of the week one had told me she was married, one said she had a boyfriend, and none of them seemed the least bit annoyed about it.
At the end of the week, I had set up dates with seven different girls, and had 12 different phone numbers. To be honest, it was a bit overwhelming. I kept forgetting which of them said what, and confused their names and other bits of information. I asked three on second dates, two of those on a third date, and only one on another date after that. In the end, I didn't end up dating any of them, but the experience was extremely valuable.
I seriously stand up straighter than I used to now, and I'm not as afraid to talk to anyone. A friend and I looked to launch a startup that would help students on campus, so I spent a day on campus surveying random students walking around between buildings. I now average about a date a week with girls I'm actually attracted to. And I really have no problem talking to anyone.
The goal I set probably isn't right for everyone, but set a goal that is right for you. Speak to one random person a day and get their contact info. Your network would grow by thousands by the end of the year (including second- and third-degree connections).