1) good study habits haha. In all seriousness though, study smart instead of studying hard. So many of my classmates studied their asses off but still struggled. We did this thing in critical thinking where we determined what types of study style worked best. Some people were visual learners while others were auditory. Cater your studying to those types of things and you should be fine. For me, I was tactile so I would write a lot of things multiple times until I recalled the information. I would also draw out diagrams and make charts.
2) I tried to study 2 hours before class. I never previewed though because that didn't work for me. I would then try to study 1 or two hours after class and finish by 12:30 or 1 am. On weekends and before tests, I'd do at least 10-12 hours and that includes all the subjects. If you study consistently, you'll find that it gets easier over time and you won't have to cram. You'll also be able to skim through the material and retain more.
3) I split it up based on what I was struggling in. The hardest subjects would be tackled first while I would go over the easiest subjects last. I made a schedule of what I wanted to finish throughout the week.
4) i found that I needed to make time to relax because I always felt like I didn't study enough. After a test, I'd completely shut my brain off and just relax with my classmates and we would go out. I also wouldn't study until I got my test scores back, but I don't recommend that part haha.