The main things that Parmesan cheese can add to a salad are fattiness and salt. The first thing that comes to mind for me is bacon. You could probably also make a yummy main dish salad (or hearty first course) by adding duck or a cured meat such as salami.
If you're not interested in adding meat, how about olives? Those would serve similar purposes. Other options might be marinated artichoke hearts or mushrooms. Just make sure you choose ones that aren't too tart, as they might add to the effect of the lemon vinaigrette.
It depends on what type of lettuce it is -- part of the issue is that if the lettuce is touching plastic, it will rot quicker, so I wrap it in paper towels, then bag it (but not sealed), and keep it in my crisper.
For whole heads of lettuce (iceburg, butter, red leaf, etc), I just wrap the whole thing in dry paper towels, then shove it back into the bag from the grocery store or farmer's market. I then pull off leaves as I need it, and re-wrap it. It stores for well over a week this way.
For mescalin mixes, arugula, or other individual leaves, I'll wash them, dry them, then unroll enough paper towels to spread the leaves on, then roll up the whole thing, and bag the roll (again, not sealed), and keep it in my crisper. I can probably get a week out of it this way.
(all times assume you're not buying from a store where it's been sitting on the shelf too long before you buy it; I get my lettuce when I can from the local farmer's market)
So, to answer the specific questions:
- keep the bag open; you don't want moisture to condense inside the bag, as it'll make the lettuce rot faster.
- I get better storage time with heads of letuce keeping them whole. If you're going to be eating it all within 2-3 days, it probably doesn't matter, and for loose lettuce, I find it more convenient to wash it as I re-pack it anyway.
- You never want to store lettuce wet ... you might be able to store it completely submerged, but damp will lead to it rotting faster.
Best Answer
Many salad packages contain freshness preservatives. That is, if the salad remains inside the original packaging, it will maintain its freshness. Regardless of the "best by" date, you should look for crispness of the greens. If the greens are crisp and smell fresh, they are good to go.