Tucking or pulling your right elbow down during the downswing causes your left elbow to move away from your body, creating an angle that leads to a slice
Allow the butt of the club to stop at impact while the clubhead continue to the finish in order to create the spin necessary to make the ball check up after a couple of bounces
Practicing at the range with a mid iron, not your driver, and if you have too steep a swing plane, practice off a tee