Good Morning Ladies ...
Welcome, KerryK ... I think the other ladies have given you a pretty good rundown about Mystery Quilts. Basically, you go with the "risk" of not knowing what you are making. They will tell you up front how much fabric and of what types you need. And as mentioned, you are told what to do with each clue, not knowing what your finished project will be like! Of course, we start guessing and for this BCS one, after Clue #1, I was guessing something with an Irish Chain feel to it .... will be interesting how I change that idea after Clue #2. And how wrong I am once completed!
Some will give clues monthly, weekly, or even hourly! There was one a few weeks ago online, that several on here did. It was a Sunday, and they posted clues about once an hour. There's one coming up on New Years Day that I might do.
And too, if you google it, you'll find several that are sitting and waiting for you to do your own pace. Resist the temptation to look ahead at the later clues and get the feel for it.