Use cold butter. The colder the better. You can even freeze the butter. As the butter melts it changes the texture of the scones. You can even make sure the bowl is cold. Don't overmix the dough. This breaks down the butter, warming it up. It is important that you don't overmix, so it is ok that there are lumps. While you can use all-purpose flour, using pastry flour is best. It makes the lightest scones. Chill the scones before baking. This will relax the gluten in the dough and that will give you a more tender, flaky scone.