Contrary to what most people believe reviewing previously learned materials is not something that is done only once.
An effective review process should be done：
The Same Day-After you finish your classes for the day take a moment and go over everything you learned， making sure to highlight any key items you want to remember. This will help you consolidate your information and make reviewing easier later on. Generally speaking it is best to focus on 5 to 9 items only to help make remembering them much easier.
The Next Day-Go back over what you learned the previous day， focusing on the key items you thought were most important. This is usually best done at the beginning of the day.
One Week Later-Go over all your lessons for the past week and summarize what you think was most important for them. Again， try to focus on 5 to 9 items.
One Month Later-Go over all your weekly studies and， again， summarize them into the most important items you wish to remember and focus on.
3-4 Months Later-Review all your previous studies for the past three to four months， focusing on your key study points as well as going back through your notes to review any other specific points you want to make sure you remember.
By following this process you will notice you will have a much easier time remembering much of what you learn and you will find your studies much more rewarding as well！