Add the whiskey, lemon juice, and simple syrup to a cocktail shaker filled with ice.
Shake until the shaker is very cold. Pour through a strainer into a glass filled with ice.
If desired, garnish with an orange slice, lemon slice, and cherry.
Notes
Always use good-quality whiskey or bourbon. My new favorite is Four Roses Kentucky straight bourbon whiskey. It is a smooth, easy-sipping whiskey with a delightful true bourbon smell.
For best results, chill the simple syrup before using it.
Store simple syrup in an airtight container in the refrigerator for up to 1 month.
Use freshly squeezed lemon juice, not that stuff in the plastic lemon.
For added flavor, mix 1 tablespoon of maple syrup into the simple syrup or, better yet, make a maple simple syrup.
Whiskey sours are typically served in an old-fashioned glass, rocks glass, or lowball glass.