It goes without saying that rule knowledge is important, but knowing NCAA mechanics is really important.
Find out if this conference uses 6 or 7 man mechanics, get that manual and find someone who already works it to help you out on the position you are going to work.
You can also buy (or borrow from someone) a tape or DVD the NCAA publishes that has a lot of mechanics boo-boos and play situations. You'll find it at their web site in this link:
http://www.ncaa.org/library/catalog/...ub_catalog.pdf