-Kimon Nicolaides The Natural Way to Draw
Designate one person to be the actor and everyone else will be artists. The actor should strike a pose and hold it for 30-60 seconds while the artist(s) draws him/her. The actor then changes the pose and holds it for 30 seconds while the artist(s) draws. Continue changing poses every 30 seconds until someone else wants a turn. Do this as long as you like. Elinor requests to do this at least once a week now. Maybe with all this practice I'll eventually improve.
The point is to capture the feel of the pose in a few strokes and not get caught up in detail, simply because there isn't time. Look for the main line of action that starts at the head and goes to the toes and draw that first. Then add other lines of movement from the arms. Try to not look at your paper, but at the actor. You can make these drawings small and do several on a page. You can practice gesture drawing with more than just people. Try to see the gesture or feel of everything. What would gesture action line would the tree outside have? Or your desk chair?