If you are looking at a rescue dog, for those in foster homes, you get a great idea of their personality before you adopt them. When I was looking, I needed to be sure the dog got along with cats as I had 7 already. Many of the foster homes have a cat or more. If they tell you "OK with children 4 and up," then it just means they have a child that age in the foster home.

Not to say a shelter dog shouldn't be considered. Depends on the shelter how much they can tell you about the dog. And on how confident you are with dogs.

Sometimes your vet will also know of available dogs. Those will also have a known history to them. Elderly who have to give up a pet to move in to senior housing, things like that. Good luck!