Wrinkly-faced dogs are cute, but those folds require regular maintenance. The folds around the mouth, or lip folds, are especially important -- they can trap saliva and other moisture, or bits of food and dirt. When things like these get trapped in the folds, it can lead to infections like lip fold pyoderma, so you have to clean out those folds to keep your dog healthy.
Dampen a clean cloth with warm water and gently wipe out the insides of your dog's facial folds, particularly the lip folds around her mouth. For a stronger clean, use a canine facial rinse containing anti-bacterial chemicals like chlorhexidine or benzoyl peroxide. The skin inside these folds is sensitive, so use a soft towel and wipe carefully to avoid irritating your dog or scaring her off.
Wipe the area again with a clean, dry towel to remove any excess moisture. If you leave the inside of the lip folds wet, bacteria can form.
Seal and lubricate the skin by dabbing a mild diaper cream or petroleum jelly on the end of a cotton swab and apply it through the folds.
Repeat this cleaning process as often as necessary -- you'll know if your dog's face begins to smell unpleasant, or if she grinds her face into the floor or furniture. You may have to do this once a week or once a day, depending on your dog and the depth of her lip folds.