I took my mountain bike, the Stumpjumper, to the bike shop today. It's rear wheel had a slight wobble that caused the rim to rub slightly against a brake shoe. The manager saw immediately that the wheel needed to be trued.
To true the wheel, he placed it in a truing stand. He spun the wheel and whenever it rubbed against the forceps on the truing stand, he either tightened or loosened a spoke to draw the rim away from the forceps. 5" later, I had true wheels.
He said a friend of his at some other bike shop placed a truing stand near his cash register with spoke wrenches draped all over it. Customers saw how to use the wrenches, and bought bunches of them. Not only did his sales of wrenches take off, but his truing business also went off becuase, inevitably, the customers would end up screwing the wheels up worse than before and would bring them back in to be trued.
Caveat emptor.