I don't know about other states, but in Michigan, precinct delegates choose state delegates at district party caucuses which choose RNC delegates. The system is set by the county party leadership (which half of is also chosen by party leadership, while other half are the republican nominees for county office which may or may not be officeholders).
I don't know which way the 7th will go. I expect Cruz to win an 8th district caucus.
I am a precinct delegate as well as the chair and I am really looking forward to going through this process.
I've never done it before and though it's a bit confusing it is going to be a great experience.