>>110632471. Man that varies so hard, depends on the semester and if it's finals week. I've had semesters where I've studied 8hours. But on average 1-4 hours. W/ 4 hours being a good study sesh to get me ready for a test.
2.
Textbook, then I gloss over the important info, hammer a few concepts in my head, then I work a shit ton of problems depending on the subject. Hours of problems if it's math or chem where I have to work at problems till they are second nature, very few problems if it's something conceptual like biology (then I spend a bit more time reading). Afterwards I go over all the information in a way that best suites the class before test day
And of course the easy A classes I read the powerpoints at most, otherwise I just show up to class.
3. Willpower is how you deal with lack of willpower, also set up limits. Say, "Ok I'm going to play this video game but not until I do a single hour of real studying otherwise I won't let myself." Also, you have to be able to say no to going out to a party on the weekend if you have a test on monday.
Last but not least enjoy yourself. Seriously, go party, go drink, play games, walk your dog, gym, play DnD, smoke with friends, read a book by yourself etc.. Living a good recreational life when you have the time will make those weeks spent studying 8+ hours a day easier. You can't study effectively if your killing yourself every semester. Only kill yourself some of the semesters and if you make it into medical residency.