Contrary to popular expectation, greens--though delicate--are a do-ahead preparation. It's important to buy first-rate greens that are crisp, not-at-all limp and without any dark brown or faded yellow spots. They can then be washed, refrigerated and crisped two to three days before serving. A lettuce spinner is a great asset, spinning most of the water from the wet greens without bruising them in the process.
Here's how to wash and crisp greens in advance:
--Wash the greens and spin or drain very well.
--Wrap drained greens in paper toweling or tea towels.
--Enclose these towel-wrapped greens in airtight (use a twist-tie) plastic bags and refrigerate them.
--If the towels become too wet during chilling, replace them with dry ones. Very wet towels accelerate spoilage of greens while just damp towels provide the perfect environment for continuing crispness.