With a grown dog, you can already see what they are like, good or bad. Grown dogs are good for people who won't be home during the day or for people without the energy for a puppy. Or maybe you just want to give a dog a second chance at life. I would have to say that the majority of dogs that are given to shelters, etc. are there not because of them, but because of their situation, so consider giving a grown dog a chance. A mixed breed.
Mixed breeds are often the happiest and healthiest dogs.
You should not buy one from a pet store or someone who happens to be selling them. Look at your local animal shelter or rescue group. Not only could you be getting the best dog of your life, you will also be saving a life. This is a list that I complied using a variety of sources. I only used the breed if every source recommended it with children.