Cleaning greens is a big deal. Cooked foods are exposed to a high temperature that kills off bacteria; therefore uncooked food is the easiest way to become ill.
How to Clean Greens
A large bowl of tepid water
Cut greens and stir into water
Make sure there is enough water in the bowl so all the greens are afloat and there are at least 2 inches of water below the flowing greens.
Lift the greens using both hands from the water and place in a container.
Touch the bottom of the bowl with your hands. If you feel grit, repeat the process.
Use either a salad spinner, paper towels, or a bag to dry the greens.
Food for Thought
Tepid water. Technically, 105° F. Tepid water and lukewarm water are alike. No need for a thermometer, this is cool water that feels a little warm to the touch.
Why Tepid? Vegetables contain oils. Oils attract the dirt. The warmth of the tepid water helps to release the dirt.
If you purchase your greens at a Farmers Market, they are not prewashed. They are going to require at least two washings.
Why float the greens? Allow the greens to float a minute. This will give the grit time to settle at the bottom of the bowl. There should be at least two inches of space so the greens aren't sitting on the grit.
Why dry greens? Because I hate water at the bottom of my salad bowl and dressing doesn't stick to wet greens.
Drying the greens. Not everybody has a salad spinner. If no salad spinner, my preference is paper towels. You can use the bag method, but paper towels are probably the cleanest item in your kitchen. I go through a lot of them.