One thing we did was to ask the Principal what our current teacher had that worked so well with our DS in 3rd grade, so that we could ask for it again in 4th grade.
She described that quality as 'Extensive Fund of knowledge' - I guess that is more socially acceptable than 'has a brain in her head' or 'has a high IQ.' So that's what we wrote down.
Other qualities that seem to be polite ways of asking for 'high IQ' teachers are 'great sense of humor' and 'able to appreciate my child's offbeat sense of humor'
'Allows a lot of assignment choice' has been useful. 'Able to tolerate persisitient questioning' has come to mind at times. 'Highly energetic' might be a good quality for a teacher to have. How about 'sure enough of his own worth so that being corrected by a student is celebrated.'
Another approach is to talk to local parents, figure out which teacher would be best, find out their teaching style, and then request that. If the best teacher does a lot of seed planting and modeling clay, then ask for the teacher with the 'hands on learning style.' If the best teacher maintains strict classroom dicipline, then your child needed 'a teacher who keeps the classroom quite.'
Good luck! A great teacher can make a great year.
Grinity