As a bartender, you will probably be asked at some point to shake a drink. The main reasons for shaking drinks are to chill a cocktail, to mix ingredients, or to put a head or froth on some cocktails.
As a general rule, you should shake all cloudy drinks (including cream drinks and sours), and you should stir all clear drinks. Never shake a cocktail that has carbonated water or soda. For some drinks, such as the Stinger or Martini, ask your guests whether they prefer them shaken or stirred.
To shake a cocktail in a Boston shaker, follow these steps:
Put some ice cubes (if called for in the recipe) in the glass container.
Add the cocktail ingredients.
Place the metal container over the glass container.
Hold the metal and glass containers together with both hands and shake with an up-and-down motion.
Make sure you always point the shaker away from your guests. That way you avoid spilling anything on them if the shaker isn't properly sealed.
The two pieces of the shaker may stick together after you shake a drink. Never bang the shaker against the bar or any other surface or object; instead, gently tap it three or four times at the point where the glass and metal containers come in contact.
When pouring or straining the cocktail, always pour from the glass container.