Any fitness instructors? Help for a newbie please

I have been asked to teach a step aerobics class at our local fitness center. I have taken step aerobics, but never taught it - or any other fitness class for that matter.

Over the last couple of months I have done numerous step aerobics classes on YouTube, searched for online tips, and created (what I thought) would be a decent music playlist. A few weeks ago I decided to start simulating a class situation. I made up a few routines and am trying to teach myself to have good form and keep up the patter for step cues and changes

My problem? I suck. I get lost, miss cues, and my footwork gets all turned around. I know in my heart I just need to practice, practice, practice, but I am getting discouraged.

So, besides having someone listen to me whine, what do I want from my fellow Dopers?

I want help.

What tips/tricks do you have or use for teaching classes?

If you are certified, by whom? What certification groups are good? What groups are not worth the paper they print the certificate on? I plan to start studying for a group trainer certification in the next few weeks and would like recommendations.

Do you have any certain music compilations you like? I lean towards 60’s 70’s and 80’s music. (I definitely have a “get off of my lawn” attitude towards most current pop music. No Psy, Justin Beiber or Beyonce please) I would love to have a playlist made up of music from my CD collection but it is impossible to keep a consistent beat.

Plus, my favorite Dope threads are first person stories. Please tell me your favorite fitness class story.