Start with a cat who has already met dogs
The strongest predictor of coping with your dog is having coped with a dog before. Ask the shelter or rescue directly which cats came from dog-owning homes or are fostered with dogs, and what the arrangement looked like — a cat who ignored a spaniel in a foster home has given you better evidence than any temperament test can. If your dog is large or bouncy, a fosterer's note that the cat lived with a similar dog is close to a guarantee that the first week will go smoothly. Kittens can also work, since they grow up treating your dog as furniture with a heartbeat, but an adult with a track record removes the gamble in a way a kitten cannot.
Read the cat's reaction to dogs at the shelter
Where the shelter allows, watch the cat's response to ordinary dog presence — a dog walked past the cattery, barking from the kennels — because you are looking for a specific middle reaction. The promising cat looks, assesses, and either returns to her food or strolls to the back of the pen at her own pace. Two reactions should slow you down: the cat who freezes rigid and stares, because that cat is flooding with stress rather than coping, and the cat who rushes the front swiping and spitting at every passing dog, because she has learned that attack is her working strategy and your dog's nose will be the target. Calm confidence, not indifference born of shutdown, is the trait to buy.
Describe your dog as honestly as the cat
Matching is a two-animal problem, and shelters can only match the dog you describe. Be specific about yours: his size and breed type, whether he has lived with a cat before and how that went, his chase response to squirrels and birds on walks, whether he can hold a settle while exciting things happen in the room, and how he greets visitors. A dog who is cat-savvy usually means one who reads a cat's warning, backs off when told, and can be called away mid-interest — if yours is friendly but deaf when aroused, say so, because the right cat for him is the extra-confident kind who holds her ground and gives clear signals rather than running, since running is what switches a borderline dog into chase mode.
Plan the home the cat will judge you by
Even the perfect match needs a house arranged in the cat's favour for the first weeks. She arrives to a room the dog cannot enter, with everything she needs, and meets the dog first by scent and by sight through a gate, exactly as you would stage any careful introduction. Give her high routes — shelves, tall scratchers, the tops of furniture — and at least one dog-proof refuge she can reach in every room, because a cat who knows she can always go up or through a cat flap into safety rarely feels the need to fight. Feed them in sight of each other but on their own sides of the barrier once both are calm, so the association being built is meals, not confrontations.
Settle it over weeks, not a weekend
Judge the match at a month, not at the first meeting. Early hissing from the cat and fascination from the dog are normal weather; what you want to see trending is relaxation — the cat crossing the room in front of the settled dog, the dog glancing at the cat and choosing his bed instead. Keep the dog on a lead for the first shared-room sessions, keep sessions short, and never leave them alone together until calm coexistence has been boring for a good while. KinsLe Messenger gathers the rescue's staged-introduction guidance, your family's session notes and any trainer's advice into one conversation thread for the cat, so everyone handling the dog that week is working from the same plan.