OMG SPINNING! I LOVE SPINNING!!!! EEEEEEEEEEEEEEE
Sorry, I'm a little too excited, because I get to go to a spin class tomorrow and I haven't been in a while. If you didn't get the hint, I really love spinning. It is a GREAT workout, burns tons of calories, but it is nice because you determine how hard you work. Therefore, as a new person you can take it a bit easy.
Things I love about spinning are: the music (turn it up loud and I hope it has a NASTY beat), getting a full hour of cardio, the exercise high afterwards, and how much the workout can vary (sometimes you turn the resistence way up, stand up, and climb really slow...and sometimes the rsistence is low and you pedal as fast as you can.)
Things to be aware of and careful for:
All instructors are different. And annoying instructor can drive you crazy if they talk too much during the class. Also, music is key. I went to a class where all they played was country, yeh, that didn't work for me. I prefer the heavy bass and club beats! So, keeping that in mind, you may want to try a few different instructors.
Also, your butt is going to hurt. Those bikes are more like road bikes than comfort bikes, but it will get better and easier if you tough it out. It is important to get set up right (you have to adjust the seat and handle bars, etc) so try to show up to class a little early and let the instructor show you how.
Finally - don't be afraid to chill out if it is too much at first. If it is way too intense, leave half way through.
Best of luck! I hope you enjoy it