So this is how I wash, dry and store my lettuce so that it is fresh and ready for salad whenever I need it! I use this method for all types of lettuce (except iceberg, see the end of this post for information about cleaning and storing iceberg lettuce) and it also works for other types of greens and hearty herbs such as parsley.
1. Fill a sink* with cold water, separate all the leaves of lettuce, place them in the water and swirl them around. If the lettuce is a bit limp, let it soak in the water for 30 minutes and it will miraculously come back to life.
2. Drain the water, turn on the faucet, and briefly rinse* each piece of lettuce as you remove it from sink and place in the basket of your salad spinner. If you use organic lettuce, just give each piece a quick once-over to check for clinging bugs and dirt. As you put the lettuce in the spinner, you can tear the leaves in half if they are large (such as full-size romaine).
3. When the spinner is full but not tightly packed, spin the lettuce until dry.
4. Spread two paper towels (still connected) on the counter and pile the dry lettuce in the middle. Wrap the paper towels around the lettuce and slide into a gallon-size zippered plastic bag. Squeeze the air out and close the bag.
5. The lettuce can now be stored in the fridge and should stay fresh for at least a couple of weeks. You can take out what you need whenever you want to make a salad or sandwich and then just reseal the bag. The plastic bags can also be reused!
*My advice would be: instead of filling the sink with cold water and then draining it afterwards, why not filling a big bowl and then reuse it watering the plants, and when is time to rinse each leaf directly with the water running from the faucet, let the water run into the bowl (the same or another) in order to not wasting water and reusing it for something else, as I said, watering the plants may be a good option.
Find the full original article here, gives a lot of other tips including salad additions and dressings, totally worth it.