Have you read Do It Now
and 10 Tips for College Students
I put lots of details in those articles.
Probably my #1 habit that made it work was that I listened to (on average) about 2 hours of motivational audio programs every day, usually while walking to/from school and between classes. I lived across the street from campus, so I was close to the school at all times. I had to constantly program my mind with a can-do, optimistic attitude. I wouldn't even allow myself to think about failure. There was only one possible outcome -- the one I wanted.
My #2 habit would have been running 3 miles every morning (about 25 minutes). This kept my metabolism high and my thinking sharp.
I also spend zero time on online forums back then, and nearly zero time on email. And I avoided getting a girlfriend or doing any dating till after graduating.
To keep track of assignments, I used a small pocket notebook. I wrote down every assignment in the notebook. When it came time to do some homework, I picked one assignment (usually the one with the nearest due-date), and I worked on it straight through till it was done. I did NOT chop up assignments or switch between one and another. If I had to do a 10-hour paper, I did it from start to finish with nothing but meal or rest breaks. Task switching has to be minimized.
I did a lot of homework during dull classes. And I ditched about 40% of my classes some weeks. If I could learn the material in 25 minutes from the book, no need to attend a 50-minute lecture.
There are tons of ways to shave time here and there.
I actually got 2 degrees in that time (math and computer science), although there's so much overlap between them that I didn't have to take many extra math classes and would have been guaranteed a math minor anyway just by picking the right CS electives.
In my last semester I was even able to add a full-time contract job while taking 37 units at school. I got used to this flow and wanted to keep pushing the limits. That was a really hard semester, but I did programming work on games projects by working out algorithms during dull classes. Or I practiced speeches while running or making food... lots of ways to double up when the mind isn't fully engaged. I was a vegetarian (but not vegan) that semester, which I do believe helped.
I was an undergrad though, and I was majoring in subjects in which I was considered a "natural." I'm not sure how well I'd have done in a different field or as a grad student.