Buying fashionable clothes that fit well is very important. There are tips and guides online about how to do it. Actual name brands can make some difference, but aren't hugely important as long as the clothes are nice.

For weight-loss I can't recommend weight-lifting enough. Not only will you lose weight, and do so quicker and less painfully than with cardio, you'll also get a bump in testosterone production for several months. This boosts confidence by a large degree. Seriously, you'll feel great.

I don't know if you know how to talk to girls, but that's probably the most important thing of all. Flirting is a skill. Unfortunately I don't know where one can go to learn this. Anyone else have resources?