It is very important to serve cocktails in the correct size glasses. Tradition does reflect on this but also most mixed drinks require a stemmed glass. The stem is used to hold the glass so no body heat doesn’t effect the contents of the glass therefore keeping it as chilled as possible.

Highball (tall) - 12 ounce - Straight or slightly slanted sides; for whisky, collin’s, julep.
Old Fashioned - 6-10 ounce - Squat, flat-bottomed sloping sides.
Liqueur - 1 ounce - Various shapes, usually small and short stemmed.
White wine - 4 ounce - Tulip-shaped bowl, elongated stem.
Red wine - 4 ounce - Rounded bowl, shorter stemmed.
Brandy - Various - Very round bowl with short stem.
Champagne - 4 ounce - Tall, slim tulip or flute shaped, stemmed.
Sherry - 2.5 ounce - Copita-tapering. tulip-curved, short stem.
Cocktail - 4 ounce - V-shaped, straight-sided, stemmed; or a wine glass.