Here are some helpful solutions for the common causes:
For a soft and fluffy biscuit, scone or shortcake, fat pieces should be the size of coarse crumbs (Think of cake or muffin crumbs, not dried bread crumbs). Learn more about Fats in Baking.
Arrange unbaked biscuits, scones or shortcakes closer together (they can almost touch) on the cookie sheet before baking. Or, bake them in metal baking pans with 1-1/2-inch or higher sides.