The first thing to determine is the winding-resistance (multimeter) The size of the
motor is a rough guide to power dissipation.
Low-impedance windings (<5 ohms) imply a chopper driver, high impedance (>20 ohms)
would suitable for a dual-H-bridge.
Putting a modest current through one winding will allow you to count the steps per
revolution, as the motor will pull towards one in four of the step positions, so for instance
a 200 step motor will exhibit 50 detentes.