The secret to cooking a steak rare is all in the touch. You poke the steak with your finger and the more it gives the rarer it is. To get a feel for it poke your stomach for rare, your thigh for medium and your breast bone for ruined/well done. The grill must be on high to sear the steak and you only flip it once. It does take practice but once you get a feel for the steak you'll never go wrong. And it is an absolute sin to cut the steak to check for rareness.