DUUUUUUUUUDE, I am the EXACT same way!! A few tips that I've found to be very helpful:

1. GET AWAY FROM THE SCREEN!! XD This might take a little longer, but in the long run it'll mean you actually get the work DONE--do everything and anything you can by hand, away from the computer, and then type it up later. Do your research online, print it out or take notes on it, and GET AWAY FROM THE COMPUTER! It's really hard, starting out, but gets easier as you make a habit of it.

2. ALWAYS write down your assignments! If you don't have an assignment notebook, calendar, or little datebook that you always keep with you, get one. FORCE yourself to look at it first thing when you get home from classes/school, so you remember what you have to do, and by when. Again, it's just forming a helpful habit.

3. Find a place where your brain is in "study mode." This place might not be your room! Your kitchen table, a local library, or your dorm's common area might be better for you to work in. If you work there consistently, your brain will automatically enter "work mode" when you sit down to work there. Make sure it's somewhere that you're comfortable, and where the lighting is good, etc.

4. Set time limits for yourself! Instead of just noodling around online for hours and hours, take a look at how much time you have, estimate how much you need for your work (overestimate! Budget more time, not less) and say, "I have till (blank) o'clock to play, then I work." Or, "I'll study for forty-five minutes, check my e-mail for ten, then study for another forty-five." Giving yourself time limits and sticking to them helps prevent aimless internet wandering, at least a little. ^.^