I teach my pups to bite in full blown social aggression in the following manner:
1) Carefully select a VERY confident pup, with genetics that reflect confidence, high prey drive, stability and health.
2) I BOND with that pup totally. He sleeps in our room, I have him nearby a bunch, take him places, play with him, etc.
3) I expose him to all kinds of surfaces and other stimuli. He must be reasonably indifferent to footing issues and sounds, smells, etc. Specially gunfire.
4) I socialize the heck out of him. ALWAYS. At kindergardens, schools, malls, etc., etc. Everyone gets to pet him. He must be friendly and outgoing.
5) For biting, I start at night. The pup's age is not important. A decoy advances SLOWLY towards me acting suspicious, from aprox 40 yds. By now the pup is looking at the decoy. I raise my voice at the decoy, the decoy yells back at me and raises a stick, eg., I give an alert command to the puppy, the decoy slightly increases his threat level, still at a far away distance...and then comes the fun part: I give the attack command and I BEAT THE CRAP OUT OF THE DECOY. The pup follows me in confusion very few times, and quickly learns to join in...via biting in social aggression. Pretty soon, the pup hears the alert command, and knows a fight is in the works, together with his boss (me). The pup and I always submit the decoy to the ground or just chase him away. We always win. If we don't, I change decoys. :lol: At about 8 months old the pups are biting a passive decoy HARD upon hearing the commands.
6) I advance from there to bite strengthening, some targeting, the out, opposition, surfaces, etc.
All inappropriate use of the teeth is corrected. All chasing is corrected (except for retrieve items). The dog is continually and intensely socialized. The dog is exercised - formally - on a mill, a bike, a pool, a spring pole, or retrieving - almost every day. I play and build up the bond with him every day.
My method works in nature with all predatory pack mammals, and we all see it. I don't know of anyone that does this as a training method. But it really works. It takes a bit longer than using a tug, but I like the results better.