the hidden ghost
When reading someone elses work, if they take too long to update, tell them that if they don't update it, you will, and that you'll do a much better job on it as well.
((You know, that's just what I've been thinking about the book series I'm reading. Not that the books are coming out too slow, but that I could write them better. A whole lot better. That's sad.))
Whenever the main character(s) realize that this particular attack/disaster is not about to hit them, but their friends/colleagues/supporters/allies (a group of minor characters), them must always be in the middle of relaying the news when the disaster strikes, killing the whole group of minor characters. The main characters can never warn them in time for even one minor character to escape.
The best ending a story can have is a heartrending farewell scene, where some of the main characters leave the world/dimension/universe forever, leaving the others behind. Best if you can imply that this parting really is for all time. Even if there is such a thing as an afterlife in your story, they’ll still manage to be apart. Best of all is if the characters had the opportunity to stay altogether, but one group of characters opts to leave (or, more likely, stay behind) for some purely selfless (and if you’re really good, pointless) reason.