Not all Yorkshire terriers sport the same coat, so there's no one-size-fits-all way to groom them. If you want to cut down on your Yorkie's greasiness, diet and grooming are the first things to adjust.
Bathe your Yorkie at least once every one or two weeks. If her coat develops an oily sheen quickly, she may need more frequent baths.
Wash her only with dog shampoos. Human shampoos or other soaps and detergents may strip her skin's natural oils a little too well—in fact, they can remove oils that keep her healthy.
Apply a special degreasing shampoo if regular dog shampoos aren't doing the trick. These thicker, creamier shampoos are specially formulated to combat greasiness, so follow the instructions on the package to cut back on her oily sheen.
Consult your veterinarian if your grooming regimen doesn't appear to help. An oily coat could be the result of a dietary issue or deficiency, which your vet can diagnose and treat by changing her food or administering supplements.