One of my clients recently brought home a brand new bundle of joy and asked for advice about integrating her with their adult dog. I thought I would take this opportunity to pass along these tips to you.
1) Scent goes a long way. Before puppy ever crosses your threshold, it's best if you start off the process by getting her used to the smells of her new companions. If you can, go ahead and give the breeder a t-shirt, towel, or other article of clothing that contains both your scent and your adult dog's scent to put in puppy's bed.
Likewise, see if you can get something from the breeder that has the puppy's scent on it and give it to your adult dog. When your adult dog is calm and relaxed just place the article in front of him and let him investigate. Later on, put it in his bed so he'll get used to the pup's smell in what is basically his "den". Dogs are very territorial about their dens so your adult dog needs to understand that puppy is part of the family not an intruder.
If you can't get an article from the breeder ahead of time, then definitely grab one when you pick up your puppy to bring her home. When she goes to bed the first night, it helps her to have the scent of her mother and littermates around her. Ideally, it would ease the separation anxiety for the puppy if she could cuddle up with your adult dog on the first night. Just see how the introduction goes and judge it from there. If the dogs don't seem to get along like old pals on the first day, don't force it at bedtime. Regardless of whether puppy ends up sleeping with the adult dog or not, you will want the puppy to sleep in your bedroom. You are the new "mama" and she needs to be close to you.
2) When you first introduce adult to puppy, do it on neutral ground. Introduce them in the park or even on the grass across the street and keep them both on a loose leash. Have the adult sit and then present the puppy's butt for him to sniff. Then just put the puppy on the ground a few feet away and let the magic happen. I wouldn't let any neighbors or random bystanders intrude on this moment. It's very important that both dogs are relaxed and that you be relaxed as well. Don't talk a lot. Don't anticipate disaster. Just tell yourself that it's the most natural moment in the world. If you notice any growling, avoidance or wariness on the adult dog's part then just separate them, correct the behavior and start walking them together down the street a little ways with each dog on either side of you. No matter what happens, avoiding yelling at all costs. Yelling only escalates the situation. I would also take the adult dog on a long walk before leaving to get the puppy so that he'll be more relaxed. And when you give the puppy affection make sure the adult gets equal attention. This is really important for the first few weeks to avoid jealousy.
3) Let puppy get used to her new surroundings. Let her sniff around your front yard before entering your home for the first time. Put your adult dog in the backyard at this point or have someone take him for a walk. Then, open the front door and let the puppy follow you in. You can encourage her with treats if necessary. Let her explore for a few minutes while still on a loose leash. Just follow her around and let her go where she wants. Then bring your adult dog in on leash. Walk both dogs from room to room. Then take them to your family area and let them off.
4) Remove any food bowls or toys from the floor as to not inspire territoriality.
5) Keep an eye on both dogs during any new situation. These include going into the backyard for the first time, guests coming over, feeding time, etc. It's situations like these that inspire dogs to get possessive.
6) Don't feed the dogs in close proximity. Place the bowls at least 6 feet apart and then remove them from the floor when the dogs finish eating.
Above all else, relax and enjoy this moment. It really is a magical thing to witness.