Good cocktail shakers can be obtained in all manner of sizes, shapes, and materials. Since metal is a better conductor of heat than glass and, therefore, the ice in a metal shaker will melt and dilute the drinks quicker than in a glass shaker, I recommend glass shakers, but with tight-fitting metal tops. The opening of the glass shaker should be large enough to take large ice cubes with ease; the opening of the metal top from which the drink is poured should be small and the construction should should be such that there will be no leakage between the shaker and the top and no drip from the top after pouring. Be sure the top is tight enough not to fly off either in shaking or in pouring, but as an extra precaution always hold one hand on the shaker and one on the top during both operations.

Chill the shaker well before using, either by leaving it in the refrigerator for a half-hour or by partially filling it with cracked ice. This ice should be discarded before mixing the cocktail. The heavier the glass in your shaker, the longer it will take to chill it, but the longer the drinks in it will stay cold and undiluted.

Every cocktail, properly so called, must contain two different types of ingredients. It also may, but need not necessarily, contain a third type. They are:

1. A base;
2. A modifying, smoothing, or aromatizing agent;
3. Additional special flavoring and coloring ingredients.

Let us consider them in order.

1. The Base   This is the fundamental and distinguishing ingredient of the cocktail and must always comprise more than 50 per cent of the entire volume. Indeed, with a few rare exceptions it should constitute from 75 per cent of total volume upward. Strictly speaking, the base must always consist of spirituous liquors – whisky, gin, rum, brandy, etc. [...] Within certain limits, however, it is possible to combine two (perhaps even more, but this is dangerous) liquors as a base. [...] ...the indiscriminate mixture of three or four or five different liquors is practically certain to destroy the distinguishing flavor and aroma of all and produce a result about as palatable as a blend of castor oil and gasoline.

2. The Modifying Agent   It is difficult to find a word that exactly describes this ingredient (or group of ingredients) and, for want of a better term, I have called it the modifying agent or modifier. It is this ingredient, in combination with the base of spirituous liquor, which characterizes the cocktail. Without this ingredient the base, no matter how violently shaken and how thoroughly chilled, would still not be a cocktail but would remain merely chilled liquor. Its function is to smooth down the biting sharpness of the raw liquor and, at the same time, to point up and add character to its natural flavor.

[...]

3. Special Flavoring and Coloring Agents   These include all the various cordials or liqueurs, which will be discussed later, as well as non-alcoholic fruit syrups. [...] Of all the factors involved in the mixing of cocktails, flavoring agents are undoubtedly the most abused. [...] These special flavoring agents should be measured by drops or dashes, not by ponies or jiggers. [...] Whenever you see a recipe calling for equal parts of rum, brandy, Cointreau, curaçao, and Benedictine, with a dash of absinthe, shun it as you would the very devil.

1. It must whet the appetite, not dull it. This first basic requirement of a good cocktail automatically eliminates a host of over-sweetened, over-fruit-juiced, over-egged, and over-creamed concoctions customarily found in books of cocktail recipes. For example, while an Alexander, like a glass of good port wine, may be a delightful midafternoon drink accompanying cake or chocolate cookies, nevertheless, in the sense of a pre-prandial apértif, it is definitely not a cocktail.

2. It should stimulate the mind as well as the appetite. The well-made cocktail is one of the most gracious of drinks. It pleases the senses. The shared delight of these who partake in common of this refreshing nectar breaks the ice of formal reserve. Taut nerves relax; taut muscles relax; tired eyes brighten; tongues loosen; friendships deepen; the whole world becomes a better place in which to live. But don't expect these results if you serve bitter drinks, syrupy drinks, watery drinks, or drinks that taste like reconditioned tin.

3. It must be pleasing to the palate. In order that a cocktail may satisfy both requirements 1 and 3, it must be dry (i.e., not sweet), yet smooth. Indeed in compounding a cocktail, the first thought should be the production of a drink sufficiently dry to wake up and energize the taste buds, yet not so sour or so bitter or so aromatic as to be unpalatable.

4. It must be pleasing to the eye. This requires no conscious effort, yet I have seen Martinis that looked like dishwater just recovering from a bad case of jaundice and Manhattans that resembled nothing else quite so much as rusty sludge from the radiator of a Model-T Ford.

5. It must have sufficient alcoholic flavor to be readily distinguishable from papaya juice, yet must not assault the palate with the force of an atomic bomb.

6. Finally, (and remember I am speaking now of cocktails only and not apértif wines) it must be well iced. Of this, more later.