Start by selecting the cocktail glass in which you plan to serve the drink – this could be anything from a martini glass to a rocks glass, although the latter will definitely work better. Place your glass of choice in the refrigerator, and allow it to stay in there for around 15 minutes, so the glass can develop a misted, frosted exterior.
Meanwhile, grab a cocktail shaker, and fill a little more than a quarter of it with crushed ice. Once this is done, proceed to pour 1 1/2 oz of fresh lemon juice, 1 1/2 oz of whiskey and 3/4 oz of sugar syrup over the crushed ice in the cocktail shaker.
Now, screw on the lid of the cocktail shaker tightly, grasp it firmly, and give it a couple of vigorous shakes. Continue shaking for around 15 seconds, until all the ingredients are properly mixed, and the drink is well-blended.
Then, take your chilled cocktail glass out of the refrigerator, hold a strainer over it, and pour the cocktail into this. Garnish the drink by plopping a maraschino cherry into it, and drop in 2-3 ice cubes too. Your Whiskey Sour cocktail is now ready – serve chilled.