Within the first couple of days of school, you are going to be bombarded with initiations to join clubs and other extra curricular activities. If your school is anything like mine, students will be coming up to you while you are eating, introduce themselves to you and basically explain why their club is the best.
It is common for freshman to not want to get involved in any activities other than parties. That is why greek life is such a big success. Greek life consists of the sororities and fraternities on your campus. Most schools don't allow you to pledge your first semester, but during that time you able to hang out with them and really get to know them.
If greek life isn't for you, there are plenty other ways to get involved at school. If you already have your major in mind, join a club that will help you excel in that topic. For instance, if you are a journalism major, get involved with the school newspaper. You get to interact with other people who have the same goals as you, and you can probably make some money out of it.