Each person has their own study habits, you really have to find the one that works best for you. I like to look over my old notes and just read the textbook as I learn by just absorbing information and have a naturally good memory, though some classes (namely foreign language and certain math classes/tests) require me to use flashcards to memorize words, formulas, etc. I'm really not the best person to ask :x
I've also found that making up songs and whatnot to memorize information is extremely helpful as well. It makes studying more entertaining, while also helping you retain the information better.
The person below me read all of the above and thinks I'm a bit too arrogant regarding studying and academics