Since I haven't thought about that (I doubt the Death will tell me I have 24 hours left D:), I would spend some minutes organizing what I'll do these last hours. First, I would write some kind of last letter about things I haven't mentioned or that people won't understand when they search in my computer. XD; Then probably I would talk to all my friends online to say goodbye, then quickly call my real life friends to arrange a last meeting sort of thing, spend some time with my girlfriend, then visit my family on both sides, and then just wait. Maybe organizing that last letter a bit more, and mentioning just everything most people don't know about me, like crazy ideas, ways of thinking, projects I've thought about, everything about me at my last moment. Then, I'd die calm.