Index cards are great but I also would use different color cards. This helped me visualize the answers better for tests. Also you can try copying your notes by hand- this forces you to read them again and by putting it down on paper you can't zone out as easily. Also check out Kahn Academy online. If they offer help with the topic you're studying they are amazing at explaining things in a simplified way. Good luck.
Textbooks don't work for me either, what I do is take a index card and put the question on one side and answer on the other (1 index card per question) and keep asking yourself the question till you get it right