64 of the 132 Michigan teams will go (about half). It is based on the total points earned at your first 2 district events. There exact point total for qualifying isn't known, but my estimate is around 40. The list of qualifying teams will be posted on the Sunday after the last week of districts (Mar 29).
FiM has a website with lots of good information:
http://www.firstinmichigan.org/
(sorry, I haven't figured out how to insert that as a link)