Aim for a ratio of about 5-to-1 of eggnog to your selected spirit for the best flavor. For each 8-ounce glass, add one shot (something like this OXO Steel Double Jigger can help you measure precisely) of alcohol. If you're mixing up a punch-bowlful, stir together a one-quart carton of eggnog with 4.5 shots.
Start with about 5 cups (1,200 mL) of your favorite store-bought or homemade eggnog, and pour it into a large punch bowl or pitcher. Since this cocktail is best served chilled, start with eggnog that's very cold. If you want to adjust the quantity of the drink, just use the proportion 5 parts eggnog to 1 part liquor.