Repetition works well because it helps your brain solidify connections that are used to recall memories. When you learn something new, your brain instantly attempts to associate it with something that you already know through a process of assimilation.
Once when preparing for a Spanish test I used repetition to help me study. This technique was useful for me, because when I wrote out vocabulary words and continued to review them until the day of the test it helped me remember the words a lot easier.
