Your clothes should be loose, comfortable, and breathable. If it's cold, you might try layers you can remove as you get warmer. You'll need rain gear if the weather looks iffy, as well as a hat, sunglasses, and sunscreen to protect you from the sun -- in winter, too. Your cell phone, a useful way to track distance, might also need rain protection. Charge it up before your walk in case you need it for a map or an emergency.