Good call, it's never too early to get them squared away, I would recommend doing the same for IALA buoyage. Flash cards helped me to a point, just beware of the trap of learning the cards rather than the actual rules they're illustrating. Your best resource is definitely the people around you, if possible get your officers/shipmates/classmates to test you on it. Also I found repetition helps, just reading the rules over and over again. There is a RoR pocketbook guide which is well worth getting. On my last ship as a cadet I carried it with me all the time and flicked through it whenever I had a few minutes.
As for websites a lot of my classmates used this one http://manila2010.co.uk/oowtaster.php contains a lot of other information which is useful for Orals prep.