You can get Free Tickets the morning of the show (8:00 a.m.) at the NBC Box Office:
The Tonight Show with Jay Leno/Box Office
3000 W. Alameda Ave.
Burbank, CA 91523
All available Free Tickets are distributed to the public on a first come, first served (2) tickets per person basis the day of the show.
For more info about attending the Tonight Show with Jay Leno, click here.