To use a chef's knife, fold the curly kale over in half, hold it down on a cutting board, and use a the knife to cut off the stem.
To use a leaf stripper, insert the stem into the right sized hole and pull through to the other side.
To cut the stem from Tuscan kale, place the leaf flat on a cutting board and use a paring knife to cut the stem off.
Chop the kale to desired size- I usually prefer 1/2"-1" pieces, but you may want them bigger depending on how you are going to use them.
Place the cut kale into a container or bowl of ice water. Stir it around a bit to loosen the dirt, then use a slotted spoon to remove it to a colander. Rinse under cold water. Then, dry with a salad spinner. (if the kale isn't very dirty to begin with, you can just rinse it instead of soaking it, but soaking also helps remove some bitterness.)
Line the bottom of a container with a damp paper towel, with as much water squeezed out of it as possible. Place the washed and dried kale inside and place the lid on to make it airtight. Store in your fridge for about 1 week.