And don't be fooled when someone says "oh he's a little angel". EL D came to me with a reputation as being very destructive but never did any damage once I got him home and my current Luny had a reputation for being very nice in the house and turns out he has a severe anxiety problem and will destroy anything by the door if I leave with him loose.
So be sure to watch the pup/dog for awhile to see how s/he acts on its own and with other dogs and also pay attention to how a dog reacts to you, a stranger.