There are lots of reasons dogs wind up in shelters.

Many are puppies from unexpected or unwanted litters. Some are there because their previous owners developed allergies or moved to a place that doesn't allow dogs. Many came from loving homes. But many of the dogs in shelters have come from backgrounds of abuse, neglect, or both. These dogs can be the most loyal, loving companions you'll ever find—but they may take extra attention, patience, and love from you up front. Sometimes shelter workers or people who fostered your dog can give you some ideas of his background. But probably more often than not, although they may know the dog was mistreated, the form of mistreatment is locked in the dog's mind. Severely mistreated dogs may have special physical or nutritional needs that may follow them the rest of their lives. You need to be willing to live with these situations. If you don't know that you can tolerate the special needs, it's better that you don't even try with that dog: the last thing he needs is to have another human let him down.

Give him some space.

If you do decide to adopt an abused dog, be prepared to let him set the pace. Although he may sense that, as people go, you aren't awful, it will likely take him some time to begin to trust you. Start by just being with him in the same room. It should be dog-proofed, so there's nothing he can hurt himself on, or nothing he can damage. Have a bed in there for him. Sit quietly and read a book or watch TV while he just lies on his bed, or wanders around the room. Let him come to you.

Be very alert to his reactions.

He may not want to eat while you're in the room. If that's the case, put his food in his bowl and leave the room. Let him eat when he's comfortable. On the other hand, you may have to hand feed him to get him to eat.

Don't reach down to pet him.

He won't be able to see you and won't know what you're going to do. If he was struck or beaten in the past, you'll frighten him. Put your hand down at eye level beside his face and slowly approach him. Let him see you at all times. Let him sniff your hand. Try stroking his chin and chest first.

Know that certain things may frighten him.

Leashes, brooms, the glint of a saucepan in the kitchen—all of these may cause him to be afraid if he had bad experiences with them in the past. To the best of your ability, just go about your daily routine without paying a lot of attention to the dog. Let him know you're there, speak to him gently, but try not to put any demands on him.

Use positive reinforcement instead of negative.

This is always best with dogs, but particularly so with abused dogs. Chances are he was severely reprimanded in the past for any infraction. You will earn his trust much faster if you reward him for good behavior. When he does something wrong, redirect him as quickly as possible to a more appropriate behavior and reward him when he does what you want. It may take a few days, a few weeks, or even months of patient, consistent treatment and unconditional love on your part, but he will turn around. These dogs seem to realize that they have been saved and they will reward you by being the best, most loyal, and most loving dogs you have ever shared your life with.