Preheat your waffle iron. In the meantime prepare your batter.
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
In a medium bowl, whisk together the milk, eggs, melted butter, and vanilla extract. If your ingredients are cold, the butter may solidify into tiny chunks but that's OKAY. The important thing is that it is evenly mixed throughout.
Pour the wet mixture into the dry ingredients and mix until JUST combined. Be careful not to overmix.
Grease the waffle iron with some oil, butter, or cooking spray. Scoop the batter into the waffle iron (the exact amount depends on your waffle iron so you may need to experiment a little). Cook until golden brown and crispy, and repeat with the rest of the batter. Serve with maple syrup or your favorite waffle toppings!