If talking of head lettuce (iceberg) I place a folded paper towel in the bottom of a bowl, place the freshly washed head in the bowl and enclose in a ziplock bag then refrigerate, this works really well for me.
I buy mostly Romaine lettuce. After washing it, I shake off most of the water, and roll it in paper towels. I then put it in a large ziploc (compressing most of the air out while I zip it) and then put it in the fridge. The lettuce stays amazingly crisp and fresh for a week.