1) Neutral Ground
I will start with one the most important tip of the video. Do not let the dogs meet in your appartment or on your yard. It is the territory of your current dog and he or she might see it as an intrusion of their territory and they might be very protective. You can go to your favourite park, but the best would be a place, which is unknown for both dogs. Of course, you will need an assistance of another person, who will bring the second dog here.
2) Act normally
Its important that you have the situation under control, but you should not be stressed about it. I know, this is easier to say than do. I would suggest you, to do ordinary things with the new and old dog. Lets say you met outside, your friend brought the new dog and you brought the current dog. Let the dogs see each other, if you want to be safe, keep them on leash, and go for a walk with them. Most likely, the dogs will be curious about each other and you should slowly let them introduce each other naturally.
Especially if you are buying a young dog or your current dog is very active, it is better if the dogs will be exhausted. Hyperactive puppy might be too much for an adult dog and he might not like the overflowing energy. Exhausted dog is relaxed dog. And introducing a relaxed dog will be much easier.
4) Slow Pace
Dont push the introduction, proceed calmly and slowly. You should be absolutely relaxed, so the dogs can see there is nothing to be worry about. If you will see no bad behaviour, you can let the dogs sniff each other.
5) Choose the correct dogs
You can make the introducing much easier, if your new dogs personality will be compatible with the current dogs personality. It is very hard to do it when you are buying a puppy, but if you are adopting an adult dog, you can ask in the shelter about the dogs personality. If your current dog is very calm and likes to relax in its pet bed during the day, you will have much easier job if you adopt another calm dog.
6) One by one
If you currently own more than one dog, dont introduce the new dog to the whole pack at one time. It is better to introduce every dog one by one. It might be completely overwhelming, if you will just throw the new dog between several other dogs that know each other.
7) Body language
You should monitor the all introduction and do not let the dogs leave alone. The most important is to be aware of the body language. The good sign would be loose body movements, relaxed open mouths and playfulness. On the other hand, you should be aware if the dogs are stiff and slow, if the hair is standing on their back, if they growl, baring their teeths or if they stare at each other for long time. In that case you should bring the attention of the dogs to you and try to introduce them after some time again.
8) Personal objects
When you arrive home with the new dog, make sure that he or she has its own food bowl, pet bed and toys. This is especially important, if your current dog is possesive. You can let them eat in different rooms, if you are afraid that they would fight. The food creates competition, which creates stress, and we dont want to have stressed dogs in our pack. It might be a good idea to hide all the old toys for some time and buy some new toys for all the dogs, so there is no competition over that either.
9) House Tour
Put the dog on the leash and again, slowly and calmly, show the newcomer his new home. Show him where he will sleep, where the other dogs live and set up the boundaries. You can do easily by closing some rooms, or you can use some baby gates.
10) Be patient
Patience is the key with almost everything you do with your dogs and introducing a new dog to the pack is no exception. And if you feel you have been patient enough, just be patient a little bit more. Sometimes the new dog will become friendly with your current dogs fast and quick, but sometimes it takes some time. So be patient, dont push it and always be calm and relaxed around the dogs.