It is usual for me to include vegetable salad in our menu if I'm cooking something fried. That is so that we can eat something healthy too. But the lettuce tends to wilt easily. And here are some pointers that I got:
Purchase whole heads of lettuce because they stay fresh longer than buying loose leaves or those pre-packed ones. And before buying check the leaves, they shouldn't have brown discoloration.
When storing make sure that the vegetable can breathe. Lack of air makes it wilt faster. So store it in perforated bags or poke some holes into the plastic.
Before serving, wash them, then dry the leaves with a paper towel. If there are any left-overs wrap them in paper towel and store in perforated bag.
So there. Some tips to make your green leafy vegetable last longer.