A full, detailed clear listing of supplies to bring to the class...including if your machine and extension cord will be required (remember to tell them to bring their power cord, foot pedal and bobbins...surprising how many don't). If you think they will have a problem getting the supplies, have a "class kit" available for purchase. I'd rather have a lower class fee and use my equipment/supplies than to be forced to buy what they demand you use. (for a "learning class...not a "project specific" class).
If you want to do samples, have them make up "sandwiches" before class by giving detailed instructions on how to do so OR have the sandwiches pre-made and hand them out at the beginning of each demo...it takes too much time for them to be made during the class.
Have stenciled designs already traced on muslin if you are going to follow designs. You can have a step by step demo of how to do the stencil but don't take the time for everyone to trace them during class.
Be sure any of your "short cut" tools are available to purchase at the shop. Show off your "can't do withouts" and be willing to let them be handled and passed around.
NO drinks, smoking, cell phones or children in the classroom.
If you are game, practice your entire class lesson on a neighbor/friend pretending they are your class. Be serious about it and have them give you honest feedback.
Have fun and best wishes.