make sure everyone can see and hear (assuming the students have normal vision and hearing)
if the class will be very large, perhaps have an assistant?
will this be a "do in class" or "lecture" type of class?
If a "do in class", have the room set up so you can get to each participant and see what she/he is doing - if necessary
will you be needing an ironing board?
check out the space you'll be using ahead of time so you know what you will be working in