THERE can be 120 dogs here at any one time: that's 120 dogs with back stories and potential, 120 dogs that need walked and brushed and clapped and, hopefully, rehomed. There are 120 dogs waiting for something - it's depressing and inspiring at the same time.

Today, the Dog Trust's rehoming and training centre at Uddingston in Glasgow is below the full capacity with around 70 residents. You can hear them occasionally through the wall. Sometimes they bark together like a discordant choir; other times one individual goes for a solo. It's worth a try.

For John Paul Maguire, this is all pretty familiar stuff. John Paul is 36 and has worked here for eight years, first as a canine carer - a general dog factotum who does all the daily chores - and now as one of the coaches in the Dogs Trust Dog School.

Today I've brought my dog, Molly, to see how she gets on and we're not even two minutes in the door and she's already showing me up, pulling at the lead and barking at nothing. John Paul has a little pouch of dog treats strapped to his waist and within a few seconds Molly is doing what she's told.

It's obvious straight away that John Paul has a great rapport with dogs - he talks softly, slowly but firmly - and, interestingly, he believes much of that came from his background. There were never a lot of pets around when he was a child growing up in the north of Glasgow, but he was one of eight children and at one point was sharing a room with two of his brothers. "Looking back," he says, "it gave me a good understanding of the need to respect space so I understand that a lot easier with dogs."

John Paul says there are a number of common problems he sees when owners and their dogs come through the door - pulling on the lead is one and not coming back when called is another. But he says the training process is about looking at the dog and working out the priorities. Is the dog displaying certain behaviour because it feels a certain way?

Another challenge to tackle is the fact that, as humans, we are considerably worse at communicating than dogs are. Dogs use a range of body movements and signals to communicate, but the signs are often quick and subtle, meaning that owners can miss them. "Look at the entire picture first, things like how they hold their ear, their tail, is it tense, is it relaxed?" says John Paul. "Are they scratching, are they lip licking because they are anxious? Paw-lifts are another one - if a dog lifts their paw, that can be to say 'slow down a second' and it's up to the person to say: 'is it my approach that is causing this?' and respond in the right way. Dogs will often communicate extremely well and as humans, we are slower."

The training technique used by John Paul and his colleagues is based on reward - the dog does the right thing, it gets a treat - but, again, it is often the owner's behaviour that needs to change. One of the main problems John Paul sees is inconsistency from owners. "If you're inconsistent with your dog, the dog is saying 'what is it you actually want?' Owners can also sometimes use visual clues to mean different things, such as pointing. The dog could follow the point, but if we point at them and say 'sit' or point at them and say nothing, the dog won't know what you want."

The Dog Trust sessions to tackle these issues and more take five weeks but the real work is done at home between the dog and its owner. The trust also does educational work in schools and communities in an attempt to improve the relationship between dogs and their owners and, in the longer term, reduce the problem of dogs ending up in the rehoming centre.

The most common reason for dogs to end up there is "behavioural problems", but John Paul and his colleagues are aiming for a day when owners will be more able to tackle the problems as they arise when they take on a dog. In other words, they would like to see owners do be much more prepared before they take on a dog to make sure they are making the right choice. That way, fewer dogs would end up in the kennels here, looking mournfully out through the glass.

When he walks along the rows of kennels, says John Paul, he sees all the individual personalities and the best days are always the ones when the dogs find a new home. Contrary to popular belief, it is not always the most beautiful dogs that find a home first, although John Paul does regret the fact that so many people come into the centre asking for a dog that looks a certain way. The Dog Trust's job is to help them find the right dog instead. "Some folk will come in and say 'this is what I want' but the carers might say 'have you considered this breed or dog instead?"

John Paul's advice is to do your research before you get a dog and then get the dog trained, whether you do it at home yourself or come to a centre like the one at Uddingston. As for his own dog, he is a lively cross-breed called Branston and John Paul knows how to handle him. But just as importantly, John Paul also knows when to chill out and stop giving the orders. Sometimes, he says, a dog just needs to be a dog.

For more information about the Dogs Trust Dog School, email glasgowdogschool@dogstrust.org.uk or call 0141 773 5130