Make sure your pet is fully vaccinated and dewormed. Your pet should go to the vet yearly for an annual check up.
Feed your pet a balanced diet with the correct nutrients, minerals and vitamins.
In times of stress consider giving a vitamin and immune supplement e.g moving house, travelling, introducing a new family member or when you are building or doing renovations.
Make sure your pet gets some form of exercise daily. Even 10-15 minutes around the block is better than nothing.