Some probing with an ohmeter, followed by some simple driver code on your microprocessor and you'll be stepping in style.
step 1Get to Know Steppers
First step is to figure out if it's a unipolar or bipolar motor. Have a look at Jones on Steppers for some deeper background, then at Ian Harries' Site for a simple method to figure out an unknown motor.
Read up a bit, then join me in a walkthrough of this motor I got for cheap. (They're on sale for $0.99 right now. They're small, relatively light, but don't have much torque. Don't know what it'll be good for yet.)