Planning to introduce a second male dog to your household? Or maybe you just want your boy to play nice with other male dogs when you run into them at the local park. Young puppies usually get along with everybody, but as they grow up, hormones kick in -- and fights are a very real possibility. Want to prevent that? Get to work on it right now.
Neuter your boy -- or boys, if both are yours. Talk to your vet about the best age to do it, if your puppy is young. Neutering alters male dog behavior -- your pup will no longer see other male dogs as competition for the lady dogs out there in the world. And as hormones go down, so does the need to fight and dominate other males.
Let the dogs figure out who's the alpha. Although you should be the leader of the pack, the pups will still battle it out for position No. 2. Some dogs are naturally submissive, so this might only take a few growls and snaps before they decide to agree on who's the boss. Or you might end up with two dogs who will absolutely not agree on being in third place and might be in constant war for months or years to come. Unless the fights get ugly, let them work things out -- it will be quicker and you won't be seen as "showing favorites."
Respect whatever order they've chosen. Once "top dog" has been declared, treat him as that. Top dog gets food first, gets petted first and gets walked first -- unless you can do everything at once. Break the rules and the top dog will be forced to put the other male "in his place" because you're not doing your job. This doesn't mean one dog gets more love than the other -- they just get it in a particular order.
Socialize your dogs. If you take Fido to the park or for a walk, he's likely to run into other males -- both neutered and not. Your boy needs to learn to behave in those occasions. Don't let him try to hump the other dog and no butt-sniffing for more than just a few seconds, and only if the other dog is not growling and showing teeth.
If you're adopting and have a choice, adopt a female. Dogs of opposite sex are much less likely to fight.