When I didn't knew how to do the test next day, I use to sleep without studying it. Next morning wake up early, go to my friend's room wake him up and ask him to hit me with questions. Because he wakes up without knowing what to ask, he use to ask random questions, which if I answer incorrectly I read them and the ones I get right I kept in mind.
Almost all the time those sort of questions use to come.
I guess I was lucky!