[sweet_tikka]

I have only ever owned male dogs [7 of them]... we just got our first girl Easter Sunday.
Because of hormones, growth, etc you will be safe to do it at 1yr, they also say behavioural problems in male dogs usually come from being neutered under the 6 month mark... don't take my word for that though it's just something a few vets have told me and I know not everyone experiences it.

BUT the humping may not stop. My 3 year old pom still humps and he's been neutered for 2 years. I've never had any other males hump after being neutered... so just depends on the dog.
Pooter has also learned the word "not okay" and he'll stop as soon as I say that and usually doesn't do it again [for some time.]