Dogs will primarily use their left nostrils for good smells

On the surface, your dog's nose may look wet, wrinkled, and cute, but your pup's nose is actually a pretty powerful device. When a dog picks up on a scent, it'll normally start sniffing with it's right nostril, then keep it there if the smell could signal danger, but they'll shift to the left side for something pleasant, like food or a mating partner.