Well you have been to class and listen to the teacher.. So why can't you remember anything they said next week? Yet alone in the exams!
Fortunately for you there has been a lot of research in this field (and it just so happens Classmaster.io corresponds a lot with it!)
If you only want to cram before a exam, odds are it won't go to well. But if you want to really understand the subject and master the exam/topic then here is how to go about it.
What was really interesting from the research is what corresponds to a good or bad revision technique and how they have scored each.