As I do with many threads, I'll start by saying "it depends" Are they coming for a short period of time, i.e. dinner and a movie, something like that, or actually staying with me over night or longer?
Short-term: house is picked up, no clutter, and depending on how long its been since I last did it, dusting/vacuuming done, bathroom cleaned (aside from the tub/shower) and kitchen cleaned and floor mopped. Clean guest towels in the bathroom too.
Long-term, as in overnight. All of the above, plust clean sheets and bath towels. I live in a 1BR apt, so any guest sleeps on the air mattress or couch. But bedding is always ready to go.
Generally speaking, due to me having very little free time, any guest is planned, so I generally have time to clean and get ready. I almost never have people drop by on a whim, so that's not usually an issue. I'm kind of slobby so if they did, I might run around and chuck stuff in my BR and close the door, just so as not too look like a total slob!