Jeez...third post this morning...what is up with me...I am usually the silent type.

I have done some good, bad, and ugly spin classes myself...and am a spin instructor. I gather the question is not how to teach a spin class, but how to *take* one. As a student, what I find helpful is a class where you don't feel overcoached, and one where you are not left adrift or unmotivated.
Find a class that has good music, quality bikes, and instructors that won't hurt you, then be motivated to get your heart rate up, then recover, then push it up again (be it by increasing resistance or increasing the cadence, or both)...hopefully the instructor will set the enviornment for this, but not demand that you do jumps, be in or out of the saddle, or whatever.

Spinning can be wildly detrimental to your body if you cycle badly, are out of the saddle for longer than you can physically sustain, or you use bad technique with a lot of resistance on the wheel. Let your heart rate tell you that you are working hard enough (or loafing).

One thing I *NEVER* do regardless of teaching or being a student...do NOT do jumps with too little resistance on the wheel or do fast jumps. In fact, the gym where I taught would not let us do them. Too many knee blowouts. I do do slow up downs, but to mid tension and mid tempo time only.

I don't spin much during the good weather when I am riding outside...but when I do, I am picky about the class I take. Hard to relax with hideous music, goofy instructors, and poor equipment. If all that is OK, it is easy to close your eyes, zen out, and get a decent indoor workout.