confidence is a definite must! but if you want to start getting more attention from girls, as in them approaching you consider changing up your wardrobe. I don't know how your current style is or what kind of hair cut you have but just look around at the type of girls you wanna attract and dress accordingly. personally I love any guy in snap backs and jordans and fitted pants and diamond supply but that may not be your style. I also like guys with fitted pants and nice polos if there like the clean cut type. its all about self expression. I think that's the best way to attract a person at first sight.
Confidence and charm are the key. (: My fiance isn't all that cute and certainly not that tall, yet we're engaged! Be charming. Woo her. Have enough confidence to face rejection. That's hot, you approaching girls way out of your league thinking you have a chance and in the end there's a 50/50 chance. Either you do or you don't. You're bound to get them hooked on you soon! Plus, intelligence is very attractive, in fact that's just what some girls look for. Don't take it as "Oh, I'm a nerd :/ " take it as yeah, I'm that smart genius :) lol I know that's definitely a turn off for me if guys are dumb! Or act like they're dumb and they're really smart! That's a huge turn off! Use what you have!
get a nice haircut, wear clothes that fit well and aren't old and worn out looking, try a nice cologne, be clean!, walk straight and confident, and really personality is key. Every guy I have dated has been average looking but its his personality that makes me like him! trust me you can find someone based on how you carry yourself rather then how you look.
have confidence don't call yourself ugly..nerds are cute usually if they have glasses and don't worry now when you get older you can always grow into your looks and your 18 so don't worry..plus there's always nerd girls
make sure you look pretty sharp all the time, have nice hair (it doesn't even have to have a great style, just soft is good). Also, when around friends or meeting girls, don't make it seem like dating is your priority.