The best advice I can give on this is, once it's done, to put it away until you can read it with new eyes. Finish the short story, print it out, then put it in a drawer and write other things. When you're ready, pick it up and read it, as if you've never read it before. If there are things you aren't satisfied with as a reader, go in and fix them as a writer: that's revision.
Neil GaimanOne of the great things about humor is, you can slip things past people with humor, you can use it as a sweetener. So you can actually tell them things, give them messages, get terribly, terribly serious and terribly, terribly dark, and because there are jokes in there, they'll go along with you, and they'll travel a lot further along with you than they would otherwise.
Neil GaimanThe Time Lords really didn't like genocide. I'm not too keen on it myself. It's the potential you're killing off. What if, one day, there was a good Dalek? What if...
Neil Gaiman