Besides making sure that the dog walker has the right training and experience, you may want to ask them what type of dog breeds they have cared for, if they would be walking your dog alone or with other dogs, and if they've ever had to handle an emergency situation. Be sure to discuss a backup plan if there is ever an emergency with your pet. It's also a good idea to schedule a meet and greet at a public place to see how the dog walker interacts with your dog, and if your dog likes that person, too!