The point to talking would be to get to know them so they feel comfortable with you and maybe even like you. The perk to talking to a lot of different girls is, you tend to stay in touch with the ones who like you and you have stuff in common with. So from the large pool you start with, you end up a couple weeks later with a few chicks who are interested enough to get to know you. Spend time talking to them more in social situations and resteraunts, you want to try to make them laugh and feel good around you so they like you. If they like you enough they will have sex with you, and if they like you a whole lot they will have sex with you on a regular basis. Being romantic helps, I know you may think it's mushy, but it will damn sure get you laid on a daily basis. (romantic does not mean poetry, a good sweeping kiss where you dip the girl down and hold the back of her head...whew that one is always a winner, and if your not that close, then just compliment her)
It is ok to like the girl back, in fact it is kind of impolite not to return the affection. If you don't seem to like her as much as she likes you, protocal is to let her go. It isn't fair to use someone's emotions to get stuff out of them and it's bad karma. If you act like a cad word will get around fast and you will be dateless for the rest of your school career. Remember...ugly girls have fine friends so be nice to everybody.