Full-grain leather: Wipe clean with a damp cloth and let it air-dry away from direct heat. Condition it now and then with a leather conditioner to keep it supple. The leather will darken and soften as your dog wears it.
Climbing rope & nylon: Hand wash in cool water with a mild soap and hang to dry.
Waterproof PVC: Rinse with fresh water after the beach, lake or mud and wipe dry.
Check the hardware and stitching regularly, and replace any collar or leash that shows wear.