You can makes notes (Either condense what you have to learn, or only right down the bits you really can't remember). I like to condense, then when I go back to it, I try to condense those notes and so on until you get it.
You can make flashcards with questions, which care always nice. Like say you had a fact you had to remember: 'The chemical formula of salt is NaCl'. On one side write 'What is the chemical formula of salt?' and the other write 'NaCl'.
You can also try past paper/past questions to test your knowledge and see if it's sticking. Also shows you where you need to improve, or where you're doing fine.
Working in groups helps, as you can learn together or test each other.
I'm sure there's many other ways to learn o/