How long should I expect character creation to take? It's my first time playing, and the other players don't know the rules yet.

For one-shot games, I heartily recommend (full or partly) pre-generated characters. We were discussing just this issue on a Story-Games thread.

If you're dead-set on creating characters at the table, I suggest a firm hand in keeping everyone on pace. If you just make copies of the Origin process and hand them out, most players will take hours to come up with four Aspects. I suggest that you throw out each question in the Origin process, and then urge the group to discuss it. Don't sit back as a disinterested party, either. Gently press people who are indecisive. Ask them to decide between two options. Let them know that if they don't like their decision, they can rewrite it later. Comic books do that all the time!

Oh, and *do* keep them to four Aspects maximum, for a one-shot. More than that never come into play. They can have as many as they like on the Scratch Pad, but just four actually in play.