Preheat oven to 425 degrees F. with rack in upper portion of oven. Line a baking sheet with parchment paper.
Mix together the flour, salt, baking powder and sugar.
Work the butter into the flour mixture using your fingers, a fork or pastry blender....you want an evenly crumbly mixture like breadcrumbs.
Mixing quickly and gently, drizzle in milk until you have made a cohesive dough. If the mixture seems dry and won't come together, don't keep working it, drizzle in enough milk - up to an additional 2 tablespoons to make it cohesive.
Place the dough on a lightly floured work surface. Pat it into a rough rectangle about 3/4" thick. Fold it into thirds like a letter and roll gently with a floured rolling pin until the dough is 3/4" thick again.
Cut the dough into circles with a 2 3/8" biscuit cutter or cut the dough into squares or diamonds with a bench knife or sharp knife.
Place the biscuits bottom side up on your prepared baking sheet; turning them over like this yields biscuits with nice smooth tops. Brush the biscuits with milk, to enhance browning.
Bake the biscuits for 15 to 20 minutes, until they're lightly browned. Remove from oven and serve warm.