One of my pet peeves is left-over food. If it has been opened, I don't want it. And if it hasn't been opened and isn't a bottle of beer, I probably still don't want it. I find that having to sort through others' food and toss it makes me very grumpy.
People seem to appreciate having that and a few other things clarified in writing, alongside the wifi code and the other details they commonly want to know.
On the flip side, I used to list "don't worry about stripping the sheets" but some people seem to want to. So now I write "if you have time, it would be nice if you stripped the sheets and put them in the laundry hamper." I figure--if this makes them happy, who am I to get in their way?