We begin by warming up, which includes stretching, and backward and forward rolling. Students roll at their appropriate skill level.
The instructor usually has a theme or focus for the class. It might be a particular technique, a particular aspect of techniques, a particular group of techniques, or whatever the instructor believes is a good focus for the students that day. The instructor does a short demonstration. The students practice what the instructor demonstrated with each other. Beginners and experienced students train with each other. This gives the newer students the chance to work on the basic moves, and allows the experienced students to develop to a deeper level. This demonstration and practice sequence is repeated multiple times during a class, allowing students at all levels to ask questions and develop.
This is not a strict format. Classes vary significantly depending on the instructor or focus.