In a large bowl, sift together flour, baking powder, baking soda, and salt. With a pastry blender or two knives, cut in vegetable shortening or butter until particles are the size of small peas. Make a well in the center of the ingredients. Add milk, all at once, into the well; stir just until dough sticks together and is free from sides bowl.
On a lightly flour surface, knead dough gently about 10 to 15 times (do not over knead or the biscuits will be tough).
Gently roll or pat dough to 1-inch thickness. Cut with a floured 2- or 3-inch biscuit cutter or a drinking glass that has been dipped in flour. Place onto an ungreased baking sheet, close together for soft-sided biscuits or 1-inch apart for crisp-sided ones. Prick biscuits with a fork.
Bake 5 minutes; reduce oven to 400 degrees F. and bake another 8 to 10 minutes or until golden brown. Remove from oven and serve warm.
Notes: If you need to hold the uncooked biscuits, the cut dough rounds can be refrigerated for up to 1 hour. The vegetable shortening or butter MUST be very cold! If you find yourself short of buttermilk for your recipe, you can make your own by adding 2 tablespoons of vinegar to 2 cups of whole milk.