It's been awhile since I took a class but I do like learning from someone who is organized and knowledgeable rather than someone who knows a little something and wants to share more off the cuff. The teachers I liked best would have their samples ready, pieces cut for every stage of the process and show exactly what needed to be done at each stage. If you watch Fons & Porter's show this is what Marianne and Mary do, with sections put together ahead of time. I know it's a lot of preparation but it works.
I took a class one time and it might be that a friend from my quilting bee was teaching it, but it was the class I liked the least of any ever. She explained whatever it was then grabbed what I had started and did half of my project to show how that part was done, then gave it to me to finish instead of having her own sample ready. It's a wall hanging of an angel that fits perfect in a space on my wall, so I see it every day. And I still notice all the time how her section is slightly different from mine. No one else would know, but I know.