At UM (Like PSU, must be a BIG 10 thing) you definately do not get dressed up for games. All you see are Maize (yellow), Blue and White Michigan apparel.
As far as The Greeks go, sororities and fraternities pair up (Its usually with your Greek Week partner) and have tailgates or pre-parties as we call them. You go to the fraternity houses about 2-3 before game time and just hand there. And you wear your pre-party shirts to the games, if you're not wearing maize and blue.

Michigan Football student tickets= $18