I try to get right to three things:
1. Chords, scales, theory.
3. Arranging on the fly.
So I taught students three riffs based on blues scale. We also practiced the major scale do-sol-do. I asked them to decide what riff they would play and when they would switch.
There are 13 musicians in the room. Some are 2nd-3rd year players, 5 of the 13 are on their 3rd lesson on their instrument.