Place the lobster on a cutting board. Push a chef's knife into the cross mark on the shell between the head and body; the lobster may still move for a few seconds. Turn the lobster on its back and split it in half lengthwise with your knife or kitchen shears. Clean out the cavity. Warning: This step is messy, so have paper towels handy. Remove the rubber bands and crack the claws with the blunt edge of your knife. This will help the claw meat cook evenly on the grill.