This writeup only covers a few of the most basic techniques used by barkeeps. I cannot even attempt to explain the more psychological side of tending bar. Once again I must thank my grandfather, who was as full of knowledge as he was of love.
Glassware: Many drinks specify what type of glass works best, these suggestions should be followed whenever possible. Always use clean glassware, keeping one towel for drying and another for polishing. A stemmed glass should be used for cocktails without ice, so that the drink will not be warmed by the hand holding the glass.
How to chill a glass: Glasses should be well chilled to keep the drinks appropriately cold. Either put the glass in a refrigerator or fill it with cracked, shaved or crushed ice before mixing. When the drink is ready, empty the glass, shaking out the ice.
How to frost a glass: For frosted drinks a glass should be stored in the freezer or buried in shaved ice until it has a white, frosted look and feel. To 'sugar frost' a glass, wet the rim of a prechilled glass with a slice of lemon or lime and then dip the rim into powdered sugar.
Ice: Use lots of ice. Cubed, cracked, crushed or shaved, all ice should be fresh, clear and tasteless. Always put the ice in the mixer before pouring the drink - this way the liquids are chilled as they flow over the ice and there is no splashing. Most highballs, on-the rocks and old fashioned drinks call for ice cubes. For stirring or shaking use cracked or cubed ice, and for specialty drinks crushed or shaved ice works best.
Sugar: As with ice, put the sugar in the mixing glass before the liquor. Usually powdered sugar is used because if dissolves quickly in alcohol at low temperatures. Some claim that syrup gives certain drinks a smoother, richer taste (while dissolving just as quickly as powdered sugar). To make your own syrup add one pound of sugar to half a pint of warm water -- slowly stirring in enough water to make a pint of syrup.
How to stir:Drinks containing liquor and ingredients require stirring with ice for proper mixing. When using carbonated drinks make sure to stir gently to preserve their sparkle. Too little stirring fails to mix the drink, while too much melts the ice and ruins the drink. Also, to stir a drink containing ice cubes, poke the ice 4-5 times. This will evenly mix any and all liquors*.
How to shake: Often drinks containing fruit juices, sugar, eggs, cream or other ingredients are difficult to mix -- these should be given a quick shake. When a drink requires frothiness (such as punches and sours, as well as fruit and egg drinks) use a blender.
Using a strainer: This is key. Strain all cocktails before serving. Always use a (non-silver) metal strainer, its easiest to use one which clips to the edges of the mixing glass.
Pouring: When mixing the same cocktail for a group of people, make all the drinks in one batch. So that no one drink is stronger or weaker than the rest set up the glasses in a row and fill each glass only halfway, then go back and finish each one off.
How to float liquor: To make one liquor (usually brandy) float on top of another in the same glass pour each ingredient slowly over a teaspoon held bottom side up over the glass. The teaspoon will spread the brandy (or cordial, or liqueur) evenly over the one below without mixing the two. Another (much more difficult method) is to insert a stirring rod into the glass and then slowly pour each ingredient down the rod. Be sure to pour the ingredients in the right order (always add liquids in order of descending density)** .
Eggs: Only ever use the white of an egg (to separate the white from the yolk, break the egg and pass the yolk from one half of the shell to the other, letting the white slip into the glass). The egg always goes into the mixing glass before the liquor (allowing you to make sure its fresh). When shaking use cracked or cubed ice to break up and blend the egg with the other ingredients.
Flaming Liquor: The trick to flaming liquor (rum, gin, brandy, whiskey) is to make sure that the glass and the liquor have both been warmed. Fill a teaspoon or tablespoon with liquor of choice, heat over a flame and then set it afire. Pour the flaming liquid into the remaining liquor to light the drink.
**and much thanks to sleeping wolf