I've never had a girlfriend, so I wouldn't know. But I have female friends. Let me give you an input.
If you want to go for at least a lasting relationship. Don't bullshit yourself. Don't go after girls based of looks 9 But that can be a major factor).
1.) Look for girls that share your interest. If you have nothing in common, then besides kissing and sex and whatever couples do, what else is there? Find a girl you have something in common with, and get to know her.
2.) Don't try any of those bullshit one liners. Don't try to impress them or make bad ass walks or spout lies about yourself. its really creepy and obvious what your going for. Be yourself.
3.) Don't make it obvious. Get in a situation that causes you to interact with them. Don't smile, just act how you would with your friends.
4.)I'm not going to sugarcoat this: Be presentable. The people who say that looks don't matter are usually the ones that don't have boyfriends/ girlfriends. If your obese, lose some weight. If you have odors, fix that. If she finds you disgusting, she won't really want to date you. But remember, looks ARE VERY important. But interest and personality are key.
5.)Don't date sexy girls/boys. They usually aren't good at anything besides looking pretty, are more likely to cheat, and usually if you can't do anything for them, leave you in the dust. Probably not all are like that, but most are. So don't go by looks.
6.) Read social cues. If she feels uncomfortable, back the fuck off. If she's crying or whatever, give her space, or if you managed to know her well enough, comfort her. People don'[t really like to be bothered when there feeling depressed.
7.) Know your league. Snag boys/ girls that are at or a little above your looks. The sexy people are off limits.
8.) Don't get a girl just because everyone else has one. Look for a girl you find...special ( I know that's corny.) You'll know when the time is right.
and finnaly...the finale
9.) DON'T RUSH IT! Start of as acquaintances. Then Friends! Don't follow her everywhere? Does she walk the way you go home, chat with her! Is she eating alone, join her! BUT DON'T GO OVERBOARD! DO NOT! I REPEAT, DO NOT MOVE FAST! If you do, ITS OVER.
I hoped that helped.