The best way to keep iceberg lettuce fresh is by cutting it, washing it and storing it in an airtight container or vegetable bag, according to Eat By Date. Another option is keeping the lettuce in its original packaging and storing it in the vegetable drawer of a refrigerator.
Cut the lettuce and wash it thoroughly in water, and then dry the lettuce out before storing it. Generally, it is easiest to dry lettuce with a salad spinner. Place chopped lettuce in an airtight container and store it in the refrigerator. Typically, chopped lettuce stays fresh for around three to five days when stored properly.