Take Them for a Walk
Ideally, you should take your candidate out for a walk — and in a natural setting if the shelter will allow it. It's possible that your dog's personality will change once they are out of the shelter environment. Pay attention to the dog's energy level. If the dog is begging for more after 20 minutes of walking, you've got a dog that will want to go all day. If he seems more prone to nap than anything else, this might not be your adventure pal. If a dog seems dull or uninterested in life, try offering it toys and treats. If it brightens up, it probably has a more energetic personality than what you're seeing.