No argument to Max's discussion, however there is at least one other way, detect zero cross voltage on the phase that isnt driven, this gives you an idea of the electrical position of the rotor (for more than 2 poles this isnt the mechanical position), then you can fire the coils to give decent torque.
This is a fairly difficult thing to get right, if its one of your first projects you'll need to do some research.
If you have position feedback things are much simpler.