Housing. Provide proper shelter for your pet whether they live indoors or outdoors. Indoor pets should have their bed or crate placed in a safe and warm place that is away from drafts. Outdoor pets should have a well insulated house that is wind and waterproof and elevated off the ground so wind and moisture can't seep inside. Install a door flap to protect against drafts and gusts of wind. Extra blankets and straw will also help to increase your pet's warmth.

Food and Water. Your dog is just as likely to get dehydrated in the winter as in the summer so make sure to provide plenty of fresh water. Outdoor pets need to consume 25 to 50 percent more calories than usual because the cold weather tends to deplete their energy. Make sure to talk to your veterinarian to make sure what is right for your pet.

Antifreeze. Dogs and cats are attracted to the sweet smell and taste of antifreeze which contains ethylene glycol. A tiny lick can kill your dog or cat so make sure to check your car for leaks on your driveway or gutter. Keep containers tightly closed and clean up spills immediately.

Cats and Cars. Keep your cats indoors during the winter. Not only can outdoor cats freeze, they sometimes sleep under the hoods of cars to stay warm. When the motor is started, the cat can be injured or killed by the fan belt. Give an outdoor cat a fair chance to escape by banging loudly on the car hood before starting your car.

Warmth. If you have a short-haired breed of dog, consider getting them a sweater with a high collar or turtleneck with coverage from the base of the tail to the belly to keep them warm.

Rodenticides. Rat and mouse poisons are commonly used during the winter months. Place them out of pets reach as they can cause fatal bleeding or kidney failure in your pet.

Sources:

American Kennel Club
Houston SPCA