Owners must know the unspoken rules of the dog park, like cleaning up after their pet, being aware of aggressive animal behavior, and keeping their dog vaccinated.

Self-policing by regular visitors often ensures pets being picked up after. Owners are quick to yell for cleanups or hand out bags to wayward owners.

�People who don�t pick up after their dog is my biggest issue,� says Val Allen, 52, who frequents several Denver area dog parks with his Korean Jindo.

Some pet owners are known to ask owners with difficult or overexuberant dogs to leave, says Doug Kelley, director of Denver Animal Care and Control.

�This kind of peer pressure is one of the most unique phenomenons to develop at a dog park,� Kelley says. �The regulars don�t want to lose the privilege of having the park.�

Like proud parents, many owners want their pets to be the most friendly, well-behaved Lassie on the block.

�But not every dog is capable of playing well with others in that situation,� says Suzanne Hetts, a certified applied animal behaviorist.

Hetts cites a recent tragic situation at an Aurora, Colo., dog park. New owners of a Siberian husky took their dog to a park only to have it make an immediate beeline for a toy poodle within seconds of walking into the park.

The husky snatched the smaller dog up and violently shook it, killing it. The husky owners were fined $75.

Hetts said the owners had the husky for only two weeks. That�s not enough time for an owner to know how his or her dog will react in a park where issues of dominance, submission and prey may be strong, depending on a dog�s breed type.

In Boulder, Colo., dog parks, dogs are required to be under voice control, Kelley says. Rangers ask owners to call their dogs to them. If the animal doesn�t respond, the owner will be ticketed.

Owners should assess whether their dog is a good candidate for an off-leash park before even going there. Although experts agree that the dog has to be socialized, owners should not try to socialize them in the park, they say.

Dogs can be enrolled in puppy preschool classes or other training classes.

�It�s nice to begin with dogs in some small group settings in rising numbers before you take them to the park,� says Laurie Thornton, a veterinarian who specializes in dog and cat behavior.

And when things do get a little hairy, owners must recognize the signs when their dog is stressed.

Owners need to know about their own behavior too. Their over-reaction or under-reaction to simple dog behavior could cause more problems than it solves.

Safety, etiquette tips

Suzanne Hetts, an animal behaviorist, shares five tips on etiquette and safety at dog parks.

1. Be knowledgeable about dog body postures, communication signals and social behavior. You should be able to recognize stress, tension, fear, play, threats and aggression. Know the difference between play and real threats. Know when to intervene and when to stay out of an interaction among dogs. If you feel uninformed about canine behavior, learn more before taking your dog to a park. Harm can come to your dog if you under-react as well as over-react.

2. Have realistic expectations about your dog�s suitability for going to a dog park. If he isn�t polite or friendly with others, get help to change his behavior before you take him to a dog park. Dog parks are not a place to rehabilitate fearful or aggressive dogs or those that just don�t know how to play well with others.

3. If your dog has never been around other dogs before, don�t go to a dog park until he�s had a chance to be around other dogs in other situations so you have a better idea of how he reacts to other dogs. If you aren�t sure how your dog will behave, don�t be ashamed or embarrassed to muzzle your dog the first few times he goes to a dog park. Better safe than sorry.

4. Supervise your dog. This is not the time for you to be distracted talking with other owners or burying yourself in a book. You must monitor your dog�s activities and other dogs� behavior toward your dog. Do not take your small children or babies in strollers to a dog park. You cannot adequately supervise both dogs and kids at the same time.

5. Know how to break up a dog fight. Direct Stop, a harmless but effective citronella spray or a small hand-held air horn are your best bets. Don�t scream and yell at your dog, don�t try to pull her off by the collar or get in the middle of the fight. This only adds to the general arousal and greatly increases either the dogs�, or your, chances of injury.

Know social signals

Veterinarian Laurie Thornton says owners must be able to detect telltale signs of dog behavior. Here�s a few indicators she often tells her clients to be aware of:

1. A wagging tail indicates a willingness to interact for good or for evil. A fast wagging, happy tail is a good sign, especially if it�s accompanied by play gestures such as bowing, where the dog�s head goes down while his rear end goes up. The dog may paw at his own face or at the other dog�s face, bounce sideways and dash away to solicit a chase. A slow, deliberate wag accompanied by a stiff body posture and a glare does not portend well.

2. If you see another dog approach your dog and it does not show play gestures, you need to watch that interaction more closely. Dogs normally will sniff each other under their tail because their scent markings are located there.

3. Usually dogs who have their ears forward with a relaxed happy look are in a good place. But if their hackles are up and they are staring in a tight-mouthed, intense way, things could be about to get out of hand.

4. Showing weapons (or growling with teeth exposed) requires immediate intervention.