I've just been thinking over the fandoms I'm really drawn to, and it occurs to me that one thing they have in common is incredibly intelligent characters: Sherlock Holmes, Miles Vorkosigan, the Doctor, Batman, the Culture's Minds, Q, Agatha Heterodyne, Willow, Toshiko, Romana...
The question is, how does one go about writing characters like that? At the baseline, you've got the ones who are at the top end of human intelligence, and then you're off into the realm of the superintelligences.
I think it was Vernor Vinge who claimed that authors cannot write convincing characters who are smarter than themselves: if you could work out what a really smart person would do in a given situation, then you are as clever as that really smart person. ( The problem with this particular point of view is that authors can cheat. )
Any good ones I've missed? Any more caveats on how to deploy those three?