Adult dogs often need new homes because they had behavior problems in the former home, but many owners have to give up very good dogs for a variety of reasons. Spend time with the dog before you take it home, and make sure you are very comfortable with it. Be prepared for a lot of intensive, consistent obedience work to help shape it into a good member of the family. Before you bring a dog home, prepare your house. Picking a Perfect Puppy for tips on puppy-proofing your house.
Similar rules apply for bringing home an adult dog.
Also be sure to start out with whatever your new pup or dog is currently eating, so you'll avoid inducing diarrhea. If you're going to change the diet, always do so slowly, spending one to two weeks gradually including more of the new and less of the old diet for a smooth transition. Designate a smaller, confined, easily cleaned part of the house in which to keep your pup or dog at first. Kitchens often work best, especially since your dog will want to be part of the family activities, and should be close to where the family is. He will need time to adjust to his new surroundings before he can be trusted with larger areas of the house.