Puppyhood moves fast, and every stage brings a new set of behaviors that can catch owners off guard. Here's a real puppy timeline, from the first weeks home through adolescence, plus one habit worth building at every stage: catching and rewarding the good choices your puppy is already making.

One day your dog happily greets strangers and explores new places, and the next they seem nervous around noises, people, dogs, or unfamiliar environments.