While it's easy enough to shred lettuce, slicing it julienne-style gives you even-sized strips ideal for presentation purposes. A julienne cut, often used when dicing potatoes, is a slice that's 1/8 inch wide and 2 inches in length. To julienne lettuce, you will need to remove leaves from the lettuce head, stack and cut them into a perfect square before you start slicing them into strips. The equal-sized strips can be used for anything, from a taco bar topping to a shredded lettuce salad.
Remove the core of a head of lettuce by slamming it firmly, core-side down, onto a sturdy cutting board. Turn the lettuce upside down and pull out the core, which should have loosened with the slamming.
Tear off the leaves of the lettuce head and place them in a large bowl. Fill the bowl with cold water to wash the leaves. Drain and refill the bowl a few times to remove as much grit and dirt and possible.
Dry the lettuce leaves by spreading them out onto paper towels and blotting them with another paper towel. You can also dry the leaves in a salad spinner, if you have one.
Stack several leaves at a time as uniformly as possible on the cutting board. Trim off the edges to make a perfect square.
Cut the trimmed stack of leaves into 1/8-inch-wide strips. Slice across the strips at 2-inch intervals, so that each strip of lettuce is 1/8 inch wide and 2 inches in length. Repeat with any remaining stacks of lettuce.
If you don't want to waste any of the lettuce, you can skip trimming the ends off and still slice them into julienne strips -- they just won't be perfectly even in length.