The way I do it: First I audition them and see if they can act. If they can, I just ask general questions about availability. Then I play it by ear. Depending on the person, where they're from. Do they have transportation (depending on where you're located).
You have to know what you need, and know how you're shooting your movie. You need people who can work within your standards. Believe it or not, you might need someone to drive a car, and the actor might not have a license. If someone has to move gracefully or dance, they might look gorgeous, but have no rhythm.
I have a friend who doesn't care as much about talent as can he get them to do what he wants and needs. His material is a bit risque. So, he asks questions that give him more of a psychological profile of his talent, than of their actual talent. This way when they read his scripts they won't run for the hills. For him it works.