How to study efficiently ?

I do not wait until the last minute to study but whenever I try to study I end up studying for almost 2-3 hours for just a simple quiz! I only want to be studying for 1-2 hours per class. I use flashcards but it isn't time efficient and it isn't as helpful as I hoped. I have tried quick cramming which works until the next week when there is a review test and I forgot everything. Any good study techniques that are fast, long-term and effective?