Hi Maximus! I do most of my experimenting with my regular classes that I teach during the week. I usually put different sequences together in different ways and when one feels especially smooth, I build on it. Members will also provide feedback when they especially like (or dislike for that matter) a particular sequence. I can usually tell if something is a keeper or not just by how it feels in class. If it takes too long to teach, or loses the heart rate in the process, I throw it away. If it feels awkward and choppy, I throw it away. But if it falls right into place and keeps the flow, intensity, and interest, its a keeper.
By the time we announce a series, I generally have enough material to put together for DVD. Then certain elements have to change for DVD verses a live class so I will make those changes too. By the time we rehearse I can generally feel if something is flowing/working or not. But there is always something that doesn't quite fit in the puzzel. If I don't like something, I iron it out alone or ask the crew for input (by now they are good at knowing what I am looking for). Then I put these thoughts into action and it is usually resolved by the next rehearsal.
Thanks for asking!