There are no right answers behind this. It's really up to you. I neutered Bunk at 10 months and he looks like a baby. I have read that neutered dogs actually grow to be bigger than intact because the hormones tell the body when to stop growing, and without them they just go and go. But ask anyone and they will tell you something different.
It's really when you are comfortable, definitely between 6-12 months. Personally I wait until they are close to a year, but that's just my personal opinion.