A cocktail waitress is, quite obviously, a waitress that specializes in the serving of cocktails and other alcoholic beverages.
They've been around since the 1940s, when they started as the all-around vice retailer for movie houses, night clubs, bars, and other such places, selling cigars, cigarettes, playing cards, as well as the standard fare of alcoholic drinks. The trade still exists today but it is almost exclusively confined to strip clubs.
The job of the average cocktail waitress is to first and foremost look cute, and secondly serve drinks and other items in a somewhat flirty nature. Most modern cocktail waitresses are required to wear a loosely-defined uniform, depending on their place of employment. The uniform is typically revealing, sexy, and cute almost to the point of cartoonishness. A universal constant is the exposure of breast cleavage, which can be used as a tool of persuasion when dealing with particularly stalwart customers, but also as a method of serving drinks, in particular those that are served in test tubes, which by the end of the 1980s had become de rigueur in almost all clubs and similar establishments.
The "body shot," as it's called, involves placing the test tube drink in between the breasts of the cocktail waitress, where it is held, and then tipped into the customer's mouth. In many strip clubs, the cocktail waitresses have taken to performing fellatio-like ministrations to the test tube shot glass prior to administering it, in an attempt to make it a more memorable experience for the (usually male) customer.
Cocktail waitresses typically make between $50 and $500 (in the United States, at least) in tips per night, depending on where they work and the flow of customers. As far as I have been able to ascertain, they haven't unionized. They're a compliment to any strip club for dealing with more timid customers, and apart from being on your feet all night, the job is relatively easy, as it's merely running drinks and making change.
A good cocktail waitress will be flirty but not too forward, well-mannered, willing to put up with all kinds of horseplay and crude comments from customers, and most of all, eager to impress the customers with either their cuteness or with some special/unique trick done with the body shot that will earn them a few more dollars in tips per occurance than otherwise. Also, they will not hesitate to call for security and have you thrown out of the place if you cross the line from passive customer to aggressive jackass.
The logical step forward on the career ladder for a cocktail waitress is to move up to the position of dancer/stripper, though some prefer to remain waitresses simply because they like it better and see stripping as too much physical or psychological abuse when done regularly. The fear of sexual desensitization also is a factor. Some become bartenders, which is just about as lucrative and requires less legwork, and less direct contact with the clientele.
When asked why she wasn't a dancer herself, one particularly adorable cocktail waitress I met answered "I'm a good girl," and left it at that, so it would seem that morality does enter the picture for some waitresses, despite the "den of iniquity" atmosphere in which they work.
In a good strip club, the cocktail waitresses provide invaluable assistance in locating your chosen dancer, an encyclopedic knowledge of the club's regular music playlists, and just how to get a maximum tip from visiting businessmen/women. More often then not, they're the eyes and ears of the club they work for. They should be treated with respect, as you would any other waitress, and tipped well. Running drinks and making change in one's underwear and hose may look easy, but it's more psychologically taxing than the average customer realizes.
Above all, cocktail waitresses are women trying to eke out a living in a cold, hard world. Enjoy their services, be nice to them, and please, keep your hands to yourself.