Bartender: A dollar per drink or 15-20% of the bill is customary. Hopping over the bar and serving at least as many drinks as you were served so the bartender can rest is also fair.
Barber, Stylist, or Beautician: 15-20%. Or the dollar increase in the market value of your sexual company added by the new look, (whichever is more).
Bellman/Porter: 1-2 dollars per bag. No tip necessary if just handing them a loose pile of laundry.
Cab Driver: Calculate the number of pine tree air fresheners necessary to counterbalance the residual stench you're leaving behind combined with the odor your driver has produced since picking you up. Provide enough extra cash to cover the cost.
Call Girl: There is no obligation to tip when paying for sex, but a compliment on the new haircut that first caught your eye is common courtesy.
Dog groomer: 5-10 dollars. Or in the case of excellent service and a real connection with the animal, never pick up the dog.
Furniture Delivery Person: 5 dollars. Or a freshly groomed dog that was honestly never that loyal to begin with.
Food Delivery Person: Ideally you should tip the delivery person a Redbox DVD you have lying around the house that still has at least 12 hours until being due. Delivery person accepts responsibility for the return and any late fees.
Pharmacist: One dose of the prescribed medicine should always be offered to the acting pharmacist.
Pilot: Tipping cash to a commercial airline pilot is considered tacky, but tradition dictates at least one exiting passenger lean in toward the cockpit and give the pilot a deep open-mouth kiss.
Shoe Shiner: They will accept additional money based on the quality and level of service, but they're much more appreciative of your following the unspoken rule of singing a short, original blues song that they may take and share with other shiners during their mystical travels across this land.
Tattoo Artist: After receiving a tattoo, it is standard to present an uninked patch of your body 20% the size of your new tattoo for the artist to practice any new designs.