Make sure your steak is at room temperature. Heat a cast iron skillet or grill on high heat for a few minutes so it is very hot. Then place the steak in the skillet or grill, turn the heat down to medium high, and cook for 4 minutes, without moving it. Then flip it over using tongs and cook for another 4 minutes for rare, 5 minutes for medium rare, 6 minutes for medium. This will vary depending on how thick your steak is.