I'm just 18, can still count the girls I've kissed on one hand, but recently started a serious relationship that's going strong and well.
I'd say it depends what you are looking for.
If you're looking to be like your brother and pull lots of girls with little attachment, then the only thing to really do is to work on it. Go out clubbing, maybe have a couple of drinks, and just be bold; you don't know if you don't try. You may get rejected occassionally, but if you don't let it get you down; not everyone is looking for the same things as you, don't take it personally, you'll eventually build up some confidence, and I think that'll help alot, that's what girls often look for.
If you are looking for something more serious (like I was), then there's not much else you need to be doing; those things can't be forced or practiced and tend to just happen so just keep your head up, be positive, and don't worry that you've not randomly kissed any girls in a while, this kind of relationship (if that's what you want) is worth waiting for.
Hope that helps.