Keep an open mind. These organizations are most likely not like anything you've seen on television or in the movies, and you shouldn't judge them by what people say on campus. Though you should beware of rumors involving anything dangerous or illegal, go to the events you are invited to and embrace the opportunity to expand your social circle.
Talk to as many people as possible. You can't judge a sorority or fraternity on the basis of one or two members; after all, if you are accepted, you will be spending a substantial amount of time with the entire group. In many organizations, everybody in the group will vote on the pledges, as well. Therefore, meeting and charming as many people as you can will only help your chances of being accepted, as well as making the week more pleasurable for you.
Follow the rules. During most Rush Weeks, the biggest rule is to avoid contact with current house members outside of sanctioned activities. Though it can be tempting to avoid this rule to get closer to current members, it will only damage your reputation and your chances at acceptance in the long term. Wait until the week has finished to follow up on new friendships.
Remain genuine. Though it can be tempting to dress as a sorority girl or frat boy from the movies, you may be surprised to find what real-life Greek members wear. Similarly, don't let any acceptance or rejection change your opinion of yourself; houses are looking for very particular things in their pledges, so you should be happy for the acceptances you do receive.