Nobody finds the fairway every time, and it's not unusual to have some shots in each round that end up nestled down in the rough where at least half of the ball is below the top of the grass.
The problem we face when playing a ball from this lie is that the longer grass will "grab" the clubhead and twist it shut before impact. This grabbing action will cause the shot to come out lower and fly more to the left than a shot from the fairway.
To effectively play a ball that's nestled down in the rough, we need to take steps to minimize the twisting effect of the longer grass.
Use one or two clubs more than you normally would for a shot from the rough, depending on your lie and the thickness of the grass.
Grip down one inch for better control and hold the club a little tighter than normal with both hands.
Stand about an inch closer to the ball to initiate a steeper angle on the forward swing.
Play the ball an inch back of the center of your stance. Moving the ball back will effectively move your hands slightly ahead of the ball, helping you strike the ball sooner, before the grass has had a chance to interfere too much with the clubhead.
On the backswing, lift the club up with your arms more than you would in a normal swing. The added lift will help you create a steeper angle of approach on the forward swing, a necessity for extracting the ball from the rough. The steep angle of approach ensures that a minimal amount of grass will come between the ball and the clubface.
As you swing through the hitting area, let the club work down into the grass. A good thought is to try to take a divot so you can hit the ball solidly and with enough force to "cut" the ball out of the long grass. The idea is to maintain a slightly faster tempo on the forward swing and take a good aggressive pass at the ball, rotating your body all the way through the shot into a full finish.
Perhaps one of the best things we can do to improve your chances of escaping the rough is to replace your longest iron with a hybrid. A hybrid provides a lower center of gravity and more surface area at the sole to displace the grass that stands between you and solid contact. Because it has more surface area at the soleplate, a hybrid's clubhead and heel are less likely to catch in the grass and shut down prior to impact.