Etiquette gurus at the Emily Post Institute recommend tipping spa and salon professionals 15 to 20 percent of the cost of your facial. This scale can be adjusted based on the service quality, but a percentage-based tip should adequately reflect the overall quality of the establishment.

Some spas that provide facials actually ban tipping. Hue, in Huntington Beach, California, prides itself on "removing the tipping element" from the guest experience, to remove stress and hidden costs and to highlight the salon's professionalism.

Determine the tipping expectations of the salon or spa, and act accordingly. As the Emily Post Institute says, "A tip should always be earned. Reward good service generously and reduce the tip proportionately for indifferent or rude service"--but, by the same token, "When in doubt about whether to tip, ask in advance. In some situations, leaving a tip could be seen as demeaning."