How do I teach my dog to greet visitors politely?

Begin training a calm greeting with people your dog already knows well and finds less exciting than a genuine stranger, household members re-entering the room repeatedly, rewarding a sit or four paws on the floor each time. This lower-arousal starting point lets your dog practice the mechanics of the behavior before adding the extra excitement of an unfamiliar visitor.

Once the greeting is reliable with familiar people, recruit friends or neighbors willing to help with a few short training sessions, following the same pattern of ignoring your dog until it offers calm behavior, then rewarding warmly. Doing this deliberately with a handful of different people, rather than only ever practicing with the same one or two, builds a behavior that genuinely generalizes to real visitors.

For actual, unplanned visitor arrivals while training is still in progress, keep your dog on a lead near the door and manage the first few minutes actively rather than expecting the trained behavior to hold up perfectly under full real world pressure right away. Real visits are harder than training sessions, so some regression during this phase is completely normal.

Continue rewarding calm greetings occasionally even once the behavior seems well established, since intermittent reinforcement keeps a trained behavior strong over months and years far better than assuming training is finished once it initially succeeds. A dog that gets zero acknowledgment for good behavior indefinitely can gradually lose some of the polish built up during active training.