If you can, get to know some of the brothers before the rush begins. Try to hang out with them if they invite you somewhere. That way you get to know them and they get to know you, and you can show them why you would make a good addition to the group. You can ask around to see who are brothers and who are not if you are at a frat house. That way you can introduce yourself to the brothers, but if they aren’t friendly try not to take it too hard, it happens.
The best way to get into a frat house and get to know the guys is by telling them to have some beer ready when you stop by because you are going to be bringing some girls from the dorms. Pick girls that you don’t really expect to have a lasting friendship or relationship with, because you don’t want your girl to be around a bunch of dudes looking to score. But, getting the guys to like you is usually accomplished easily if you are able to bring girls to the house, and beer. Also, you want to have hot women that you are bringing, the hotter the better.