If you are planning on taking him to places where he must be neutered, like dog parks that have regulations on that, or doggy daycares, then you kind of will have to do it, as soon as it is required.
If you got the dog at the humane society, and they have a contract with you that you will neuter the dog within a certain time frame, then honor that contract.
If you are unable to keep your dog on your property, than six months -- before he is capable of siring a litter.
Some suggest neutering before boy-behaviors like marking and humping get a hold, 8-10 months, probably.
Structurally, many of us feel that it is better for a dog to remain intact until the growth plates close, and secondary sex characteristics have developed, 18 to 24 months.
And some of us never neuter as we feel it is healthier for the animal to remain intact, or because we feel a working dog may work better in some areas while entire, or because we intend to show the dog and the dog must have all his equipment.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC