How to get the perfect cocktail without a 007 reference.
Broadly speaking, cocktail ingredients can pretty well mix themselves.
Beyond that we more often than not do one of two things.
Shake: bring the temperature of a drink down at a rapid pace, dilute thoroughly and work a lot of air through the cocktail. Perfect for a daiquiri, an espresso martini or more indulgently any type of whiskey-ish sour.
Stir: To drop that temperature right down and add dilution slowly. What we ant to achieve here is the ability to taste as we go. Perfect for more “sophisticated” drinks that balance two or three ingredients. Namely the Martini or Old Fashioned.