Introduction: Find Bipolar Stepper Motor Coil Pairs
There is a really easy way to figure out which two sets of wired are paired on a bipolar stepper motor. Get an LED, and hold the anode and cathode to any of the motor's two electrical connections (respectively). Turn the motor shaft and see if it lights up. If it does not light up, change where the wires are connected and try again. Keep changing these pairs until one set lights up.
Once you have found a pair that lights the LED, it is fair to assume that the other pair of wires are also connected, and will also light an LED. You now have found and identified the coil pairs and can start working with the motor.
If the LED does not light up with any pairs, you can get a similar result by using a multimeter and measuring the voltage that the motor outputs when you turn the shaft.