Stepper Motor Control - Full Step not working
Read this: http://digital.ni.com/public.nsf/allkb/B1CC4C64ABBC7D3C86257BC70017B9E2

Your motor may be 4, 6, 8 wire and use of the wires may depend on the way you are configuring your driver (single ended or H-bridge for example). If you are using a ULN2003, it's highly likely you are using this type of connection with one common center connector connected to your supply for the coils:

 

You need to buzz out the wiring for your stepper motor and understand what wires connect to what coils.