How to know you are revised long enough and covered all you need to study?
Try to Explain your idea in the subject to a friend, who do not know the
topic or cannot get the idea properly. If your friend can understand it, than
it means you can catch the topic and can express your idea , and you have
studied enough. If you can explain simpler and the friend understands it quickly,
then you know better than normal. So you can adjust the level of study and
control the time and the reference material.
A study group can make study more effective, by letting a group of classmates
of same level sitting together and study together, you can get the important
ideas more quickly. Moreover, if you have something can't understand,
you can ask others in your group, so study will become more effective.