I once read in a cookbook about the best way to wash salad greens. I think it may have been one of Jaimie Oliver's books? Anyway, it said to fill a clean sink with cool water and gently place the leaves in it. Don't be rough, they can easily bruise. Turn them gently with your hands, drain in a colander. Wrap in a clean towel, store in the fridge.
Ever since reading this I use tea towels when storing most of my fruits and vegetables. I have a drawer full of them for this purpose, my red pine cone tea towel is my favorite out of the bunch. There's something nice about storing your food in cloth, like wrapping them up in a blanket.