Here's what you do:
Be physically attractive. Seriously, this is by far the #1 thing no matter what any girl here says. First of all girls are liars just as much as men are, and thus can't be trusted. Girls want to tell themselves that they like a guy for personality but it all boils down to sex. A girl will determine whether you have a likeable personality by how sexy you are, period.
Holden Caulfield said it best:
"The trouble with girls is, if they like a boy, no matter how big a bastard he is, they'll say he has an inferiority complex, and if they don't like him, no matter how nice a guy he is, or how big an inferiority complex he has, they'll say he's conceited. Even smart girls do it."
I swear to god this is the definitive guide to girls. 90% of girls will fall if you are sexy. To gain the other ten percent, here are some auxillary traits that may help:
a. money
b. having an 'individualist' attitude
c. uniqueness
d. acting like a party boy
e. having a nice car
f. being the life of the party (this one helps more than others)
NOTE: the above guide is written with girls ages 14-24 in mind. Past there, looks are still a big factor but "success" takes a big hunk of it as well.