Volleying is a lost art. There are a handful of players on the ATP and WTA tours that are extremely good at it. The majority of players tend to rely on their hands and the movement of the racquet when they volley.
Even though the game has gotten faster, your step should be part of the volley. Keep in mind that most of the time you will take only one step. There are three different types of steps that should be used.
First, if the ball is hit out wide, use the foot farthest away from the ball to step across (diagonally) moving towards the ball and the net. If the ball is hit within reach, make your step (again with the foot farthest from the ball) pretty much directly towards the net. Finally, if the ball is hit right at you, step away from the ball (with the foot farthest away) and slide the other foot in that direction.
In all of these situations, the racquet should stay out in front and there should be a very small amount of movement. Emphasize making contact with the ball as close as possible to the contact of your foot hitting the ground. This will help you time the hit and also give you some extra crispness in the volley.
Use one of these steps whenever possible!