It might already be too late to get into the Michigan State Campground of your choice for this summer. You can only make reservations up to six months in advance. The weekends are already booked up at such popular campgrounds as Grand Haven State Park which opened last week. Call 1-800-447-2757 (which is routed to Kentucky, I believe) or visit www.michigan.gov/dnr to make your reservation online. This year the non-refundable reservation fee is $8 whether you call or place your reservation online. Don't think you can save much by not making reservations.
There is still a $5 charge for those who take a chance on finding available sites and just show up at a campground the day they want a site. I wouldn't recommend doing this at all, but especially on the weekend in the summer. If you make your reservations now, you still have a great shot at finding camping sites available on weekdays and there are still weekend slots available at many of the less popular state campgrounds.