Science fiction: Space should be stranger than we can imagine. Fill it with spiders, darkness, strange metals. Do not pad it out with people talking about The Way Things Are In Our World. Put in long shadows, green suns, agate eyes, cats that walk backwards. Do not bother with rockets, space-guns, The Planet Of —–. Acceptable: Dream The Smoke As Evening Falls. Not acceptable: The Battle of The Space Rocket Vs. The Three Eyed Aliens. Witches are OK, space generals are not. Avoid sailing ships in outer space. Trans-dimensional all-powerful beings are OK, but be sure to reference them as impossible abstractions, with personalities like Oxford dons. No Captains. No First Officers. None of those floating space hotels with mysteriously convenient gravity, where the chief activity is looking out the window, and reacting to things that appear in the window.
Fantasy: For a supposedly limitless genre, this one has gotten mired in cliche up past its own asshole. So: No wizards, kings, knights, no D&D character-classes, no &*@# dragons. (so sick of dragons). Fill it with ferns that complain. Fill it with stones that build castles out of people. Introduce lovable hobbits only if you’re going to murder them messily. If you must have elves, don’t call them elves, don’t let them live in a @#* magical forest, and be sure to feed them to stoats at every opportunity. NO QUESTS! NO MAGIC THINGS TO FIND ON ANY QUESTS. Did I mention NO QUESTS? If you want mythical beasts, mythology has shelves full of beasts: mediocre fantasists run right past them on their way to the dragons. Here are some examples: chimeras, hecatonchires, brunnmigi, Amanojaku, enenra, serpopards, Peg Powler, or, hey, just make up your own. You’re supposed to be using your imagination. Why bang about in someone else’s recycled universe?