The porn, well, because it's the best way to spend a weekend if you're a loaner. Just a joke
About tutoring, I did not tutor anyone, teacher was about the last job I want to have, I simply don't have the patience. As I said, I was a used goods salesman. But several of my college friends did that. You basically pick high school subjects that have to do with your degree. If you are in literature: anything related to that. If you are in international relations: history, citizenship, politics or philosophy. If you are in something "sciency": phisics, chemestry, math... and so on.
Write an ad like this, but adapted to your case:
College studant in International Relations tutors high school studants on History, Citizenship, Politics and Philosophy.
Then post it on popular ad websites. Also, print a few and glue them on bus stops or street lamps near schools in your area. Also, speak to the people at this schools, sometimes they have message boards for people to pin ads like this.
Good luck, young enterpeneur.