This is our first garden year. My problem with fresh garden lettuce, from friends or the farmers markets, has always been it doesn't seem to keep well. Like, you better eat it the day you get it, or it's a big waste. It is super bad to waste fresh produce that a friend gives you and it's horrible to waste food you spent top $$ for at the farmers market. Speaking of saving money, we haven't bought bag lettuce in a couple months. I spent $2.50 on a little flat of 6 different little lettuces. Mike eats salad every day so we were spending $5 - $8 a week on bag lettuce. And THAT lettuce is not nutritious like mine is! Oh I just can't say enough good things. But how to keep it from going bad within hours?? I'm going to tell you.
Pick your lettuce low on the leaf, near the stalk of the plant

Bring your lettuce in and place it in a bowl of water cut side submerged for 1 or 2 hours.

Pull the lettuces out of the bowl and place it lined up neatly on a long row of (still connected) paper towel. A nice touch is to put one type all in a row, then the next type on top of that, longways, repeat with all the different lettuces. That way, when you're unrolling, you only have to unroll a little bit to get all the varieties together.

Roll up the paper towel and put it in a plastic bag and put it in the fridge. I kept this lettuce for 10 days or more. We got full use of it, none was wasted.