So, if you know any of this already, sorry.
He tells the group that he likes to start with a character, and then asks the group to more or less "vote" on whether the character is male or female. Then they "vote" on the age, and go on to other things like marital status, physical appearance and any disabilities, so on and so forth. As this develops, any possible goals for the character may crop up and be discussed as well.
Once the character and goal is decided on, they can continue with the why questions (especially why that particular goal?) and the what can go wrong questions to develop a plot.
OSC may start over again with another character (opposite sex from the first one, at least), and as the process becomes clearer to the group, he won't spend as much time developing plot as he will getting the ideas started and seeing how many different branches the group can come up with for each start. (He does this partly to encourage them to think of more than just the off-the-tops-of-their-heads answers to the questions. Things always get more interesting if he can get them to dig deeper and go for the fourth or fifth or sixth answer to a question instead of the first or second answer that they come up with.)
I hope this helps.
This is the third thing we're doing as a class (after the introduce yourself and requisite ice breaker that I have to do... *sigh*)... now I'm just hoping nobody comes to the class hoping to write poetry because I'm horrible at it (everything comes out sounding like a broadway showtune, and while that might be wonderful if I were writing Broadway showtunes... well... I'm not.
)