We do meetings quarterly in our ward.  There is someone called to coordinate that but they don't teach it, we are in charge of that part.  It is always the 2 Tuesday of the month and we do a 20 minute lesson which focuses on whatever we think is the most important thing at that time.  We get a pretty good turnout because we have stuck to our promise of only a 20 minute meeting.  May not seem like a long time but you really can cover a lot if you make it really on the target.  And I would rather have a good turnout for a short intense lesson than low attendance.  We have refreshments afterwards and stay to talk with those that have specific questions, want help, or etc....

The teaching seems to rotate among our presidency or if it is a topic that seems like it could really be delivered well by another member we think of, then we ask them.   I even had my husband teach one time.

Our motto is actually "20 minutes and a treat"  Primary workers always laugh, but they show up!