Depends on the motor, how the terminations are brought out for connection, and the size of the conductors.
Crimped ring lugs with screws/bolts are popular because you don't loose any lead length when connecting/disconnecting the wires multiple times. Downside to this method is that the connections must be wrapped in tape for insulation.
I've used these with good success in the past:
http://www.mcmaster.com/#6878k97/=u4xbbu
They're vibration resistant and rated for high temps.
I've also used these:
http://www.mcmaster.com/#7618k632/=u4xc2w
Easy to terminate, but not good if you have to join more than two conductors. They're not rated for more than one wire under a screw.
Split bolts and tape are also an option, especially with larger conductors. Again, downside to this method is that the connections must be wrapped in tape for insulation.
Some motors have terminal studs that lend themselves to using ring terminals. Those are often found on European-manufactured motors. Those are really easy to terminate.
Standard wire nuts are not a good idea, in my opinion. I've come across them multiple times on smaller motors; they were often loose from vibration and age.
SceneryDriver
