"My meat pounder has two sides- one with a smooth surface and the other looks like dinosaur scales. How do I know which side to use? "
The smooth surface of the meat pounder is the part you will probably use most often. Use the smooth surface to flatten or thin chicken and chops, or to even out thickness so they will cook evenly. The part of the meat pounder that has notches or small teeth is used to tenderize tough cuts of meat: those teeth break up the fibers which can help make it less chewy and also allow marinades to better permeate the tough protein.