Tapestry Folkdance Center in Minneapolis/St. Paul books contra callers and bands in quarterly blocs (Jan-Mar, etc.). The booking committee has caller, musician, and dancer representatives.
As with many booking committees, there are some prejudices about what constitutes quality music & calling (some of which I share, and some of which I don't -- I'm not on the committee).
Even though we've traditionally been a good-sized dance, we are not really on the way to anywhere, so we get very few out-of-town bands/callers -- maybe twice a year. Happily, we have wonderful local talent. The booking committee asks for availability about two months before the start of the quarter, then tries to fit everyone in with an emphasis on equity. The occasional traveling band or caller usually contacts us well before dates are set and can be accommodated.
I think the only band that gets special treatment is Contratopia -- their regular fiddler (who is absolutely top-notch) is a farmer in Decorah, Iowa, and does not travel anywhere from mid-April to mid-October. So they get booked more than their share in the wintertime.
I will comment that our system does tend to perpetuate the same old folks all the time and we aren't creating good pathways for up-and-coming new talent. We do now have a regular "community dance" on fifth Saturdays with open calling and open band, and that's helped. Still, I'd like to see us doing more to identify and book folks outside our standard circle.
Our monthly family dance books in two blocs, fall and spring (we don't have family dance in the summer). Similar process, but there's just one booker and a smaller set of callers and bands, because we operate on a shoestring budget and sometimes pay very little when turnout is low.
David