Unsettle your opponent
Try to do something different. Follow your instinct. You can, for example, try to distract them by standing on your line and waving your arms or jumping around from side to side with arms outstretched. Sometimes, it doesn't take much to put the penalty-taker off and force them to make an error. Think back to the shootout antics of Liverpool keeper Jerzy Dudek at the end of the 2005 UEFA Champions League final. Older fans will remember Bruce Grobbelaar and his "spaghetti legs" in the shootout that Liverpool won to claim the European Cup in 1984.
Portugal keeper Ricardo even took his gloves off during a shootout in the quarter-finals at UEFA EURO 2004.
Everyone has their own technique, but it is sometimes worth doing something out of the ordinary to knock your opponent off their stride.