We've always washed our salad greens by soaking in the sink and/or running under cold water, depending upon type of green, then spinning in a salad spinner. Spin, drain, spin again, drain! Greens are spiffy clean and less apt to wilt. By storing them in a tupperware container, they often last a week or more without spoiling. The key is the salad spinner's ability to get rid of the excess moisture, then the cold ofthe refrigerator just seems to crisp them.
If you've never used a salad spinner, they are more than worth the effort in terms of the results they produce. We often see them at yard/tag/garage/flea market sales going for a pittance because people usually classify them as not worth the effort, along with banana stands, thigh masters, and blooming onion cutters. Not so, for those of us who enjoy a lot of greens, bunnies too!
Of course, easier way is to buy the pre-washed mesculin mixes, some of which are tasty, but we like things like, arugla, mustard greens, dandelions, spinach, escarole, bok choy, cilantro, etc. in our own salads. The buns most frequently get the salad "bones" after cleaning and tearing off the leafy bits of the greens.
Buck