Add all dry ingredients (flour, baking powder, sugar, salt) to a large mixing bowl. Stir with a whisk until combined.
Add eggs to flour mixture.
Add vanilla extract to milk, then pour into flour mixture.
Using a whisk, stir to combine. Don't over mix, batter will be lumpy.
Gently stir in melted butter until just combined. Don't over mix.
Using a preheated waffle iron, add in batches and cook according to waffle iron's directions.
Notes
I use a 1 cup measuring cup to add to waffle iron. I also pull the waffle slightly before the built-in light comes on as I like my waffles a little less done.