-Talk to friends who have boarded their animals and get their recommendations first. Or, ask your vet who they recommend. You can also look at Yelp and check out the public reviews for the kennel's you're considering.
-Make sure the kennel is fully licensed and insured. Don't be afraid to ask! Check out their website to get a feel for their facility and services.
-Inspect the boarding facility yourself, both inside and out. Ask for a tour. Make sure it is clean and orderly. Bring your dog along, so they can get a feel for the place, and so you can introduce them to the boarders and share any of their quirks and general needs.
-Is the temperature comfortable? Ask what measures they take to keep the animals comfortable, especially at night.
-Dogs, especially, are creatures of habit, so ask questions about the kennel's daily routine. How often will your dog be walked? What about playtime? Is there a nap time, or quiet time? The best boarders do what they can to keep your animals socialized and active, with structured activity, so they'll have as much fun as possible in your absence.
-Will the boarder email or call you with updates or send pictures? Many boarders these days have cameras with a live stream that you can check in with to “see” your pup during play time.