Clean up after your dog. No one I know likes to step in it. If you're going to pick up your dog's and you happen see another, pick it up too.

 Pay attention to what your dog is doing. It can be easy to get distracted once you let your dog loose. If your dog is aggressive towards people or other dogs should be leashed or removed. And one time I saw a dog pee on somebody's leg. :-o

 Don't permit your dog to dig, destroy park resources, or chase wildlife.

 If you are in a park near housing, keep your dog quiet.

 Make sure your dog is current on her shots and has a valid license.

 Be careful about bring dogs or children that are too young.

 Observe and obey all park rules. Make sure you always have your dog's leash with you, and use it where necessary or when required by law.
 

Remember, a few bad dog owners ("Bad human!! Very, very bad!!) could ruin it for everyone if dog-friendly parks decided to ban dogs. Be courteous of others!