The best way to do it is to set yourself small goals, then let yourself have rewards every time you reach a goal. It’s the way I get my house cleaned on my days off when I really don’t feel like doing anything. I will also compromise. “Okay, I can fold this load of laundry while I watch an episode of Big Bang Theory, then I’ll go do the dishes, and when I’m done with that, I’ll go sit on Facebook for fifteen minutes. After that, I’ll vacuum the living room, and then I’ll take the dog out to pee and smoke a cigarette.”
When you break it all down into small goals, it’s much easier to tackle. Read, say, ten pages and take notes, then take a break and check on your Facebook or Fluther, then review what you just read or do a page of your homework. Also, it helps to have moral support. Find a friend who is good at the class in particular you need to work on, and have them come help you. They’ll help to keep you on track. Or find somebody else in your class this summer, and study with them, so you can keep each other on track.
Push comes to shove, print the information you need from the net, and then turn the computer off. Or you can actually set parental blocks that will only allow you into your social sites for a certain period of time during certain times. If you really have trouble, that might be the way to go.