It all comes down to the fitness level of your participants. One minute might be to long for a beginners class but not for an advanced level. As to the format of the exercises, there is really no best way to ago about it. You can manipulate the sequence and types of exercises anyway you like. If you have 15 people in your class you can create 15 stations and be able to have them complete 3 rounds within the 45 minutes time frame (if each exercise takes 1 minute to complete including the rest period). This question can be answered in many different ways, so you need have an idea of the goals you are trying accomplish and then decide how you want to go about it.
I hope this helps.