As you can see by the posts here, tipping is a universally diverse topic. I spent many years in the hospitality industry and have a degree in Hotel Administration from UNLV and have worked just about every position in food and beverage ranging from fast food to gourmet and fine dining. That doesn't make me an expert but I would like to offer some input based upon my training and experience. I will only address it as pertaining to the United States.

Wait staff is usually the lowest paid of all employees and are highly dependant upon their tips. Many establishments even legally lower their salary even more by a 'tip offset' that allows the employer to undercut minimum wage and factor the expected tips to approximate mimimum wage with tip income added. In most general dining situations it is customary to tip an amount of 15-18 percent on the food total before taxes and should not include alcohol, although many people tip on the booze, too.

The IRS 'levys' a standard 8 percent of a server's food sales even if the person does not make this amount in tips. If the establishment can show that the amount of tips routinely falls below 8 percent this can be reduced on a business by business basis. This was done in the 80's to try to reduce unreported tip income, a very big issue in the food and beverage industry. Their is a similar provision for those that serve ONLY beverages, such as bartenders and cocktail servers.

A basic tip is called for when you receive good service. I premium tip of around 20 percent is appropriate for excellent service. In some fancier restaurants that have captains and wine stewards that provide an additional layer of service you may see charge receipts that have additional tip lines for these people, for which 5-10 percent is appropriate.

In many union shops there are archaic tip splitting arrangements that often take an unfairly large percentage of the pool away from the food server. So it is acceptable to try to find out from management if service staff pools their tips and then you can adjust accordingly. In fact, casino dealers at the Wynn in Las Vegas recently unionized due to the polarizing affect when management tried to implement a tip pooling policy of sharing tips with salaried supervisors, previously unheard of even in that mecca of greasing the palms.

Chefs and food preparation staff do not routinely receive tips, although it is not that uncommon. Professional kitchen staff are usually the highest salaried members of the staff, often making more than managers or maitre d's. I would not recommend sending them alcoholic beverages from the bar with the exception, perhaps, of at the end of their shift, such as if you are still around at closing time. Many places have little or no tolerance for alcoholic consumption by staff. A more appropriate gesture would be a small gift card, such as for Starbucks or something like that. I have seen many posts at FT of people that do that for FAs that go above and beyond.

AND...it is totally acceptable to leave no tip at all when the service is poor or non-existent, but don't leave a few coins trying to 'send a message' as this is just rude. At the end of the day you vote with your feet and management needs to be on top of the actions of staff and poor service will kill a restaurant much quicker than the so-so food quality.

If you are a regular patron, treat the staff around the holidays the same way as you do your doorman, super, mailman, and others that you gift to (or for special occasions).

I have a thick skin after 25 years of officiating college athletics, so if I have ruffled anyone's feathers I stand ready to accept the criticism that may follow my post.