By far, the best way to remember/understand something is to relate it to yourself in some way. Along with this, once you finish reading material, you want to summarize it to yourself. If you are lacking details, you know you obviously did not learn it. Basically, don't treat everything like a homework assignment or some meaningless study material. Try to understand why things are the way they are. If you're only studying for the grade, you aren't going to learn the material on a higher level. Once again, study methods always depend upon what test you are studying for.