This came up in another group and I will post it here as well. Usually when you buy mushrooms, they are prepackaged or you can buy them bulk and loose. Either way you buy them, (If prewrapped, remove the plastic covering) wrap them up in a paper towel and place in the fridge and they will last longer.
For lettuce, core, wash and dry. Then wrap in paper towel and then wrap in saran wrap.