One effective exercise that I use is to climb to altitude and have the student fly without touching the control wheel. The only controls available are the trim, throttle, and rudder. Have the student trim the airplane so that it is flying straight and level. If the airplane begins to bank, either you or the student can level the wings with the rudder. After flying like that for a few minutes, ask the student to descend at 500 feet per minute by reducing power and trimming the airplane to that rate of descent. Then ask the student to level off at a given altitude, all of this without touching the control wheel. After the airplane is stabilized straight and level, have the student climb at a given airspeed, again using only trim and throttle. If necessary, the wings can be leveled with the rudder. Have the student level off again and go back to cruise flight, all without the control wheel.
It's a great way to teach a student the value of trim. If a student doesn't become proficient in trimming the airplane, there will be trouble ahead when he or she transitions to heavier iron. It is surprising how quickly the student will become comfortable with trimming the airplane using this exercise. Good trim technique is a skill that will make your student a less frustrated and more proficient pilot.
Richard Hiner is vice president of training for the AOPA Air Safety Foundation