If you want a jumpstart, go to your local bookstore (Barnes and Noble, Borders, etc.) and see if you can locate an NFL rulebook.
You can also go to
http://www.nfl.com/fans/rules to get some idea of the rulebook.
Here is another site
http://www.supernfl.com/NFLRules.html
[Edited by mikesears on May 20th, 2005 at 12:31 PM]