If you're planning on running a funnel, have the player generate maybe 5-6 zero-level dudes and run him through a shortened adventure. Remember that part of the purpose of the funnel is to trim the characters down to one or so and, since he has fewer total characters than a group of players would have, make sure that the adventure is short enough to do the job without killing everyone.
If you're planning on running a higher level adventure, you might allow him to pick a couple of levels from each of two classes, such as a fighter-wizard. Typical party adventures are often set up to make use of the whole spectrum of specialties that different character classes can provide, but a single class often is missing many of those specialties. (E.g. some adventures don't work well without a thief.) Allowing an easy multi-class system avoids some of this issue.
_________________Marv / FinarvynDCC Minister of Propaganda
; Deputized 6/8/11
DCC RPG playtester 2011, C&C
since 2003, ADRP
Since 1993, OD&D
player since 1975
"The worthy GM never purposely kills players' PCs, He presents opportunities for the rash and unthinking players to do that all on their own."
-- Gary Gygax
"Don't ask me what you need to hit. Just roll the die and I will let you know!"
-- Dave Arneson