Moving from a house to an apartment has a number of implications for a dog, and the owner needs to be proactive about helping the dog to adjust. Expect that your dog will need more attention from you since you will have to accompany your pet each time it needs to go out. Your dog will also likely be encountering a larger number of other dogs than usual, and depending upon your dog's personality, you may need to do some extra training. Additionally, there are also a few health considerations that you will need to address.
Preparing for the Move
Take you dog to visit the apartment complex in advance, if possible. This way the location will not be completely foreign to your dog when you move in.
Visit you vet for a checkup, and explain the situation. Make sure the dog has all his shots. If you are moving to a different state, make sure that you know if there are any different requirements in this regard. Also, ask your vet about prescribing a stronger anti-worm medication (such as Interceptor), as worms can be a significant problem in an apartment complex where there are a lot of other dogs.
Consider whether there are any new pet supplies that you might need in the apartment that you did not need before. For instance, you might need a dog bed, if your dog was sleeping outside before. Have some new toys on hand, especially if the dog will have to spend much time alone. A few extra boxes of treats won't hurt either. Purchase a supply of poop bags to clean up after your dog. If your dog tends to be aggressive to other dogs or people, then get a muzzle.
Get your dog's nails trimmed and filed. This reduces the likelihood of your dog scratching up the walls and doors.
After the Move
Do not leave the dog alone in the apartment for the first few days, if possible. Noises from neighboring apartments may frighten your dog and cause him to bark excessively. When you do leave your dog alone for the first time or two, ask the next door neighbors to let you know if your dog barks, so that you can address the problem if there is one.
Take your dog out for walks regularly. If possible, take your dog on at least two 20 to 30 minute walks per day, along with any needed bathroom breaks. This helps ensure that your dog is getting enough exercise, so that he is calmer in the apartment.
Take your dog for a short walk in the evening before bedtime, and make sure he relieves himself. This helps avoid having to take him out for an emergency walk in the middle of the night.
Let your dog have some alone time on the balcony from time to time. However, be prepared to bring him back in if he starts barking at passers by.