Has your four-legged friend become more of a four-legged enemy? Perhaps you've been on the wrong wavelength, writes Dave Thomas

One of my dogs, a terrier called Macy, has become a difficult two-year-old. She is impossible to walk, as she pulls on her lead constantly. In the garden she has dug up plants, chewed decking and eaten trellises. And she pounces on visitors. What can I do? Getting rid of her is not an option: Macy is part of the family. According to Clare Deignan, a canine-behaviour consultant, the problem is communication: we need to understand each other better.

When she calls to my house she explains that she does not blame owners for their dogs' behaviour. Blame implies you knew what you were doing from the start, she says, but people don't know how to communicate in a way their dogs will understand.

There are, she adds, many ways to deal with separation anxiety, aggression, lead-pulling, being afraid of strangers, jumping on people and other common problems.

I introduce Deignan to Macy and my other dog, Jackson. Both pounce on her as she tries to sit down. She stands up immediately, so the dogs slip off: the best way to solve jumping is to ignore it. This can be difficult, particularly if you are wearing good clothes or are carrying shopping bags. "It goes back to communicating with the dog," says Deignan.

"A lot of people will giggle, shout or push the dog away, but the dog is still getting some form of attention for bad behaviour. Ignoring the dog tells him that there is no reward for bad behaviour. The dog may try a little harder for a while to get the attention, just giving it one last try, but in time it will learn it doesn't work."

The rule to remember is that you should reward good behaviour and do the opposite for bad - which means not punishment but no reward.

What about taking her for a walk? So far, says Deignan, Macy has been in control. Don't use a choke chain, she says - a "complete no-no" that can do great damage. Instead, use a harmless harness or head collar. "The harness and head collar makes walking easier, but it will not change the behaviour." So I now have to stop the walk if Macy pulls on the lead, waiting until it goes slack again before continuing. This way she will learn she is going nowhere if she pulls. You can feel silly, moving only two or three steps at a time. But as Deignan says: "What happens here is that you are not shouting or yanking the lead. All you are doing is communicating with them in a way they will understand."

Dog owners will say it is impossible to have a nice back garden, as dogs will chew, dig and trample plants. I try spraying a solution of crushed garlic over the plants, as aversion therapy. It doesn't work. Then I try sprinkling chilli powder over them. The garden takes on the most amazing colour and aroma - but Macy enjoys eating the chilli-covered ferns. "Again, you have to think: What is the dog getting out of it? She is obviously having fun," laughs Deignan.

The plan she leaves me says to distract Macy with her toys when I catch her digging. There are some great toys that allow you to hide food in them, which set the dog a mental and physical challenge. Playing with them can be far more fun - and far more tasty - than playing with soil and plants.

Perhaps you have a puppy that is becoming troublesome. It may leave puddles on the floor, smelly surprises behind the kitchen chair and teeth marks on the table legs. The key to a well- behaved adult dog, according to Deignan, is to begin training it as a puppy. Toilet training is easy, she says. Even if you do nothing they will learn to go outside and find a spot to do their business in. "What happens is that people contribute to their bad behaviour by rubbing their nose in the urine. It's really very ineffective."

So start training when the pup arrives in the house. Learn the signals it gives when it needs to go to the toilet. Dogs usually need to go first thing in the morning, last thing at night and shortly after they have eaten. So at those times take them into the garden, pick a corner and keep them there until they relieve themselves. Then give them a treat.

Problems can also occur if a dog and its owner are mismatched. If some pets are deprived of mental and physical stimulation they can become destructive, noisy and aggressive. If you have a small back garden, don't get a big dog. Read up on breeds first. Pick one that suits your lifestyle: if you don't want to go for lots of walks, then get a basset hound - or a cat.

If you get a puppy you have between eight and 20 weeks to get it used to all sorts of situations - meeting people, cats and other dogs, for example, or coping with the noise of traffic - that will help avoid problems in the future. Consulting a specialist such as Deignan can also help, leaving you and your pet to enjoy each other for years to come.

Clare Deignan, who is based in Co Wicklow, is at 087-9283456. The irishanimals.ie website has details of several other specialists. For help training dogs you could also visit the ISPCA website (www.ispca.ie) or call 043-25035