Leeks are grown in sandy soil.  Most tutorials talk about slicing a leek lengthwise, removing the root and dark green portions, and rinsing the exposed portion under water.  This is appropriate if you're grilling or roasting the halved leek as a dish in and of itself, but a much CLEANER and very easy way to clean leeks if they are an ingredient is to fill a bowl with cold water, slice off the root and dark green, cut the leak in half lengthwise, then lay the cut sides down on a cutting board and slice through the leeks at 1/4 to 1/2 inch intervals.  Dump the slices into the water and swoosh around with your hands, let them sit and settle, then gently lift out the floating leeks and see all of the dirt at the bottom of the bowl!    If you're sauteeing you can just lay them on a towel or paper towels to drain; if they're going into a soup or stew just dump them right in - the extra moisture won't harm a thing.  Here's to "clean eating"!  For more tips and tidbits you can subscribe to Lula's blog here.