People who know nothing about dog behaviour sometimes flee from perfectly harmless dogs who have no intention of hurting them, because they operate under the belief that everything on four legs is just waiting to attack them.

That same attitude is sometimes directed against bigger dogs by people who are only familiar with toy-breed dogs – they think all medium-to-large dogs are vicious.

But most pet dogs who come up to you on neutral ground are harmless. They just want to sniff, check things out and perhaps make friends. A friendly dog will trot up in a relaxed or curious manner, may wag its tail and have its tongue hanging out, and lean towards you or your dog for a sniff.

If you encounter an aggressive animal running loose, or a territorial stray, or if you trespass on property patrolled by a fierce dog, the signs it will display are very different from those of a friendly one saying hello.

A dog intending to bite out of aggression or fear may stay unusually still at first, or bare its teeth, growl, raise the hair on the back of its neck, and move in a stiff-legged manner. It may circle you, or charge. It may flatten its ears, but stiffly, unlike the soft lowering of the ears of a dog happy to greet its owners.

If you know little about dogs and want to make friends with one being walked by its owner, let it sniff you. Don’t immediately try to pat it on the head, as it may think you are about to hit it.

Extend the back of your hand towards it (to protect your fingers, just in case), at the level of its nose or lower, and let it check you out. If it sniffs you and turns away, it’s not interested. Let it alone. If it wags its tail, licks you and paws at your legs, it’s friendly.

Read the signs. Act appropriately.