From the Book “Cream Rises” people remember the first thing and the last thing they did in class so make those two things fun. I lead boot camp style classes so I can do play ground type games, lot’s of times we finish with a relay race of some sort. Google “ice breaker games” for ideas. Good Luck.
I’ve found the best way to win class participants over is to shower them with knowledge, organization, compliments (when appropriate),and fun…basically the best damn class they’ve ever done! You want them to feel so good, that they will have no problem getting into the new groove. Also it doesn’t hurt, if you can, to incorporate some of the moves/tone of the previous class (can make for a good transition).
An additional suggestion: have only good things to say about the instructor you are replacing, regardless of whether people are critical or praising in comparison. Be open to suggestions by the participants. Even as you are creating a new format, if there are things they liked before, I am sure there is a way of somehow incorporating it.
And – if you are good at this – try to learn the names of the participants. You will soon find that there are a few who set the tone and can make or break a change.