I haven't taken advantage of this in the past, but I plan on scooping up some seats for family members for games such as UWM, Gtown and Ville before they go on sale to the general public.
My memory may fail me, but I think a form comes in the mail with your tickets.
True .. MU normally mails out a form for STH's to buy extras .. but it can also be done on ticketmaster.com. I like the TM route, as I believe that's the only way you can have your tickets electronic .. meaning you can email them later, if need be.
From the MU website:
HOME GAMES
Individual tickets will go on sale for season ticket holders on October 13, 2007. Individual tickets go on sale to the general public on October 27, 2007.