Meredith Townsend DeVoe
One of the most important points when mixing pancake batter, and where people mess them up, is overmixing the batter. You should stir ONLY until ingredients are mostly incorporated; there may even be specks of dry flour (these will bake out) and NOT ONE SECOND MORE or they become rubbery and heavy. 
If you want to add blueberries or other things, toss them with the dry ingredients, then add the milk and egg mixture.