flyguy,
First off review the recovery from a normal stall (power on or off). Then introduce to the student what may happen when the stall recovery is not executed properly; ex. increase back pressure too rapidly before the airplane has a chance to gain airspeed. There really is no difference between a normal stall and secondary stall. However knowing the correct technique to recover from a secondary stall and preventing a secondary stall from occuring could save his/her life.
Show them the order in which your control surfaces will be ineffective during a stall.
E-elevator
A-aileron
R-Rudder
During a stall your rudder is the last surface to become ineffective, instill that in your student so they which surface is going to give them the best performance and also so they can make a safer recovery. Hope this helps a little. Good Luck!!