1. Mulch around your greens. Mulch prevents rain from splashing soilborne bacteria onto the leaves. Bacteria make the greens more susceptible to rot before and after harvest.
2. Harvest in the morning. At this time of day, the leaves' cells are full of water and have the best texture. Wait until the dew has dried.
3. Poke a few holes in the bag and place a dry towel in it. The plastic creates a humid environment by preventing the greens from losing moisture to the air. Poking holes allows a bit of oxygen into the bag; the towel soaks up condensation and helps keep humidity high.
4. Fill the bag loosely and don't seal it tightly. Packing the greens tightly bruises and breaks the leaves, making them prone to rot. Leaving the seal slightly open allows more oxygen to enter.
5. Store in the crisper. It's the coolest part of your fridge.
6. Wash and spin. Unless your greens are really dirty, it is best to wait and wash them right before serving, because it is hard to get them completely dry, even with a salad spinner.