In a large mixing bowl, whisk together the dry ingredients: flour, sugar, baking powder, and salt. Set aside.
In a separate medium-sized mixing bowl, whisk together the wet ingredients: milk, melted butter, eggs, and vanilla extract.
Pour the wet ingredients into the bowl with the dry ingredients, and gently mix until just combined. Be careful not to overmix the batter; it's okay if there are a few lumps.
Preheat your waffle iron according to the manufacturer's instructions. Once heated, lightly spray the waffle iron with non-stick cooking spray.
Pour a portion of the waffle batter onto the center of the waffle iron (the amount will depend on the size of your waffle iron; usually around ½ to ¾ cup). Close the lid and cook the waffle until golden brown and crisp, usually between 3-5 minutes, depending on your waffle iron's settings.
Carefully remove the cooked waffle from the iron using a fork or tongs, and place it on a wire rack to cool slightly. This will help to maintain the waffle's crispiness. Repeat the cooking process with the remaining batter.
Serve the waffles warm with your choice of toppings, such as maple syrup, whipped cream, fresh fruit, or a dusting of powdered sugar.