Preheat your oven to 350°F (175°C).
In a bowl, whisk together flour, baking soda, and salt.
In another bowl, cream the softened butter with brown and granulated sugar.
Add eggs and vanilla to the butter mixture, mixing until well blended.
Gradually add the dry ingredients to the wet ingredients.
Fold in your choice of mix-ins.
Drop tablespoon-sized balls of dough onto a baking sheet lined with parchment paper.
Space them about 2 inches apart.
Bake in the preheated oven for 12-15 minutes or until golden.
Remove from the oven and let them cool on a wire rack.