Adopting a dog from a Humane Society, or a private shelter, can be a great gift to the dogs fighting for survival on the streets, abandoned by owners, or mistreated before they were rescued. However, this should not be done naively, or with the heart alone. Any new purchase of a dog needs to be done carefully, and not on impulse. There is nothing worse, for the family or the dog, to take a dog into your care and then discover that problems arise which you are unable to handle. This ultimately contributes to the sad fate of abandoned dogs.
There are many factors to consider when thinking about getting a new pet. There are the ongoing costs of food, vet bills from routine operations like desexing and minor illnesses or mishaps, as well as the time and money involved in training dogs. Depending on your experience with dogs, you may need to take your dog along to an obedience school. Dogs need to be trained so that they know how to behave around people, to prevent any biting or aggressive behaviour around neighbors or small children, and to establish a harmonious and understanding relationship with their owners. Many of the reasons people abandon dogs and other pets can be avoided if they take the time to train their dog, and understand where the behaviours that exasperate come from - and what to do about them. That is responsible dog ownership.
One of the advantages of adopting a dog from a shelter or humane society is that the animal will usually be desexed. Despite some lingering mythology around the subject, desexing does not psychologically or developmentally harm the dog in any way. That is a projection of a human response onto an animal of a completely different species.
Some private dog shelters have a 'No Kill' policy. This means that unlike many others that euthanase a dog if they are not rehomed within a certain period of time, these shelters place dogs in foster homes until a new owner is found. The advantage of adopting a dog from one of these places is that the temperament of the dog will be more well known. Plus, many of the behavioral issues that can come from the trauma of being abandoned, or being abused, are healed in a loving environment by the foster carer before the dog is available for adoption. Things like how well a dog interacts with other dogs will generally be known, which is essential if you have a multi-pet household.
No Kill shelters also rehabilitate very sick or malnourished dogs before they are put up for adoption. Most shelters and humane societies check a dog's health before letting them get adopted, so you at least know what you are getting in to. They can also provide advice on whether a dog is suitable for a more experienced dog owner, whether a dog is suitable for a family, and can provide tips on how to smoothly integrate a dog into a new household.
To decide to adopt a dog is a very noble thing to do, especially given the huge number of unwanted dogs in the world. As well as that, by adopting a dog from a shelter, you're actually helping that shelter help other animals. Whilst these dogs are not free, the charge is nominal, and generally covers health care costs for the dog. Many dogs may be given away free 'to a good home', but going this path is risky. You won't know if the dog has a serious or contagious illness, which can be a disaster if you have other pets. Plus, you won't get unbiased advice on that dog's temperament, or history. Many times these owners really just want to get rid of the dogs in their care, and not all are scrupulous about to whom they give the dogs to.