Well, you may not know exactly that someone is right for you. Try to find someone who you have something in common with, and WORK for that relationship. Call her and invite her to hang out often. Bring her treats if she's sick. Make her feel special and loved, and she'll reciprocate
Just try to find someone you 'click' with on a personal level and have interests in common with. But if you don't end up with the girl you wanted, DON'T give up! She and you can still have a great relationship. It happened with my first little and me; I barely knew her, but now we're very close.