Make sure your dog is well trained and easily controlled.
Always hold the leash by the handle, NEVER by the cord/belt. Holding the cord/belt while it's retracting may cause injury.
Once attached, extend the leash to a comfortable walking distance.
Make sure your dog isn't so far that you can't pull them back in a hazardous situation!
If you think your dog may encounter a hazardous situation, keep your dog close to your side with the brake pressed and the leash extended to only a short length.
DO NOT give the leash too much slack. This could harm you and your dog of they decide to bolt off somewhere!
If your leash gets wet during your walk, extend the leash to it's maximum length to let it dry.
Let your dog rest during and after your walk if they have to, especially if it's hot!
Above all, make sure to enjoy yourself! This is quality time that you get to spend with your beloved pet.