I generally use romaine lettuce - so I don't know if it would work other types of lettuce.  I cut the stem off at the bottom, wash the leaves and let air dry - then I reassemble the lettuce into the "romaine shape" wrap in paper towels and store in crisper.  The lettuce is washed so you can use it immediately and it seems to last as long as if you didn't cut off the stemp or wash it.  

I found if I washed and tore up for salad it would go rotten within a day or two.  By keeping it whole it lasts longer. 

Just a tip .  I like the idea that I can make a salad at moments notice/ no washing/no drying just eating :)

We generally use the bags of prepared salad makings.   I find that when I put a folded paper towel inside the package it will last for days longer than if I hadn't.. (The paper towel draws out the moisture.)

I can't stress to you how great those little green bags are!!  They really do work.  But like you said, I think the lettuce stays better if it is still in tact.

Thanks for the great suggestions. I will definitely be trying them. Another item I have found extremely useful is the produce keeper containers from Tupperware. My neighbor sells Tupperware and they had a promo for the produce keepers last year - BOGO. So I bought two large ones for $20 and gave my mom one. We are both amazed at how much longer our produce keeps when we put it in the container.