Remove any tight plastic wrapping from whole lettuce. Place in a large container or loose open bag. If its chopped lettuce, open a small hole in the bag at a corner.
Store the lettuce in the fridge. To minimize access to moisture make sure to store lettuce in the vegetable drawer or crisper drawer of your fridge. Storing lettuce alongside other fridge foods runs the risk that the leaves will absorb moisture from them leading to soggy lettuce heads.
Reduce moisture build up. A paper towel works great for absorbing excess moisture. Place a single sheet alongside your lettuce in the fridge and replace in about 5-7 days.