I wouldn't recommend my study habits to anyone but it works for me just fine.
With studying, I always do as much as is needed and as little as possible. And that may be, compared to other people, considered as doing very much studying.
In high-school, I didn't really study that much for everyday stuff. School was boring, everything was so easy, I went there, somehow got my things done, I graduated. I rarely did any homework at home, I managed to get it done at school or did it at the beginning of the next class. When I had to study for a test, I prepared a concise overview of the subject a few days before the test, went trough the material and aced the test/exam. I remember not even opening a single book to study for my final exams, I just went there to wing it, I was really sick of all the high school stuff.
I hate the feeling that I HAVE to study, that puts me off every time, so I'm a really lousy student because I only study for the tests/exams to get the credit points and be done with it. But since I have to do it in the university, I always prepare and there's no way I'm going to fail a class because doing the studying again and re-taking an exam/whatever is not an option. I value my time and sanity too much.
I can memorize things very easily when I write things through or see them (I can't call it eidetic memory because I have to make a conscious effort to memorize them by repetition over a fairly long time). I have to make an effort to really listen to the lecturers because my mind tends to wander and I can remember very little when I hear something in a lecture, unless it's something really funny or very interesting. In the university, when you have like 5 different lectures/seminars in a row in one day (one lasting 1,5 hours, with 30 minute breaks in-between), you get the feeling that it's best to get rid of all that junk in your brain the moment the lecture has ended.
With simpler subjects or subjects I happen to like, it's all about going through the material and winging it during the tests/exams. Then the pressure is off and things are really easy to remember.
This is what I do with subjects that are more difficult and not that interesting to me and have loads of material:
So, I usually go to all of the lectures and write down everything that I feel is important. I rarely go through any recommended additional material, unless it's a class I really like and I'm really interested in the subject. At the end of the semester, a few weeks before the exam, I go through all of the materials I wrote down, I get rid of all the unnecessary junk and prepare like 10 A4 or more pages of concise information, covering the most important aspects of the subject.
This is where things go crazy for other people

But not for me. A few days before the exam I have to have complete silence, total concentration and I memorize those 10 or more pages line by line. It's not numb cramming because I have to make everything understandable to myself and I create all sorts of connections and visualize the text as I go through it, so in the end, I can recite the whole 10 pages by heart with no problems.
I never do all-nighters, and the most excruciating studying I had was for a really disgusting subject. 8 days straight, 10 hours a day, gnawing myself through the materials

I wouldn't even recommend it to my worst enemy.
I feel that I have to do it with subjects I hate because I really get stuck/mind freeze when I can't remember the exact fact or I can only remember that I've seen it somewhere but can't exactly remember what it was and it's all downhill from there. So, during the exam, when I've memorized it all, I can access the information like different files in a computer, it's all hovering before my eyes. I have complete control over my memory.
It's an ineffective method when you're supposed to remember all the stuff after you take an exam, and that's exactly what makes me a lousy student because I get rid of the stuff the second I hand down the exam paper. But when you have like 10 exams to think about, it gets really disgusting and all you care about at that time is passing them.