I believe in waiting as long as possible but not TOO long, perhaps before or after the first heat. Maybe at or around a year of age. My experiences with neutering/spaying before they are sexually mature have not been good experiences. As long as the owner is RESPONSIBLE and can keep their dog under control (especially females, if you choose to wait until after the first heat) then I feel that is best.

This is just MY opinion, however.

Of course early spaying for medical or health reasons (as in, retained testicles, etc) I am for.

Males and females fixed before they are sexually mature don't ever seem to be as sound physically as those who were fixed after their sexual maturity. I guess this is just an issue for show dogs though. If they're pets it probably doesn't matter either way