I love avocados, but they definitely have to be handled with care. You have to eat them when they're just ripe — when the skin gives slightly to the touch — and ideally, you shouldn't peel an avocado until right before you plan to eat it or it will turn brown and mushy.
But what if you want to cut open an avocado, slice some off, and store the rest overnight? Or, perhaps you've made a big batch of guacamole a few hours before a party, and you don't want it to turn brown? Simple: Just store the avocado or the guacamole with the pit. To store a sliced avocado, simply return the pit to its spot, re-cover the avocado with its skin, and wrap the fruit tightly with cling wrap. The same trick works for guac: Just nestle a few avocado pits into a bowl full of guacamole and store refrigerated under plastic wrap. Sure, it will still turn brown eventually, but saving the pit will extend the avocado's life tremendously.