Everyone knows that excellent service deserves a gratuity. The modern gentleman knows that an excellent gratuity often guarantees even more excellent service in the future. The extra $10 you grease a valet gets your car parked up front for a night, but the $50 you grease him gets you that treatment for a long time to come...certainly much more than your next couple trips.

"In our world, we view the holiday season as a way of saying, 'I appreciate you'. That's a nice tradition," according to Peter Post, a great-grandson of the late etiquette maven Emily Post. We couldn't agree more.

So what to tip your favorite service providers? A common rule of thumb is the equivalent of what you would pay that person for a day or a week or a month of service. Some examples:

• Your barber: Cost of one haircut or a gift
• Mail Carrier: Gift valued at up to $20
• Babysitter: One evening's pay
• New York Times deliverer: $10-$30
• Favorite Shoe Shiner: $10-$30
• Housekeeper/Cleaner: One day's pay
• Haberdasher: Nothing - just keep supporting us!

Do keep in mind, however, that some professionals may not be able to accept certain gifts. Mail carriers, for example, cannot accept cash, but they can accept a gift of up to $20 (Truefitt & Hill Shave Cream anyone?). Some teachers, doctors, and nurses have similar guidelines. Evidently, Las Vegas bouncers have no limit to the gifts they'll accept.