The easiest way to check if a steak is cooked is to use a meat thermometer. Insert the thermometer into the thickest part of the steak and check the temperature.  Rare steak should be cooked to an internal temperature of 125 degrees, medium-rare should be cooked to 135 degrees, and medium should be cooked to 145 degrees.  Another way to check if a steak is done is by looking at the color of the meat. Rare steak will be red in the center, while medium-rare will be pink. Medium steak will be brown throughout, and well-done steak will be dark brown or black.  Finally, you can check for doneness by pressing on the steak with your finger. A rare steak will feel soft, while a medium-rare steak will feel slightly firm.  A medium steak will feel firm, and a well-done steak will feel hard.  While this is less reliable than using a thermometer, with a little practice you can get it right every time.