Summarize this article in one sentence.
To be sure you aren't ingesting any dirt or pesticides, always wash produce before you prepare it. If the lettuce is marked “ready-to-eat,” the FDA has certified that it is clean and can be eaten as it is, but some experts recommend washing it again when you get home.  Remove the outer layers of leaves, until you get to a layer where you can't see any visible dirt or wilted edges. Grasp the entire head of lettuce and run it under running water. Gently scrub the exterior of the lettuce with your fingers to remove any traces of dirt or pesticides. Do not soak your lettuce in a sink filled with water – this will not remove the dirt. The stalk of the lettuce tends to be tough and can have a bitter taste. Remove the pale, hard tip of the head and discard it. Also discard any of the outer leaves that appear wilted or discolored. Put the lettuce on a clean chopping board and use a sharp kitchen knife to cut the head in half, through the root (or stalk). A classic chef's knife with an 8 to 10 inch (20 – 25 cm) blade is recommended for chopping lettuce and most other vegetables. Set each half of the lettuce, cut side down, on the cutting board. Slice each half in half, through the root (stalk). Place the lettuce quarter-section on the cutting board with the outer leaves against the board and the cut edges facing up.  Position the knife at the far, right edge of the lettuce and begin cutting with a back and forth sawing motion until you reach the cutting board. Move over approximately 1/4-inch and begin sawing again. The last piece of the head segment may be too small to slice safely. Reposition the small piece on the cutting board so that it lays flat, and finish slicing. Move onto the other half of the lettuce if a lot of shredded lettuce is desired. Slice only what you will need for your meal, and return the remaining uncut portions of lettuce to the refrigerator. Shredded lettuce will brown and wilt more quickly than lettuce that is left intact.

Summary:
Wash the lettuce. Remove the tip of the lettuce head. Cut the head of lettuce in half. Cut the head into quarters. Shred the quarter head into thin slices. Shred another quarter, if needed.