Actually, I prefer what Harlan Ellison said: "I don't want realism, I want verisimilitude." Not reality, but truth. What SEEMS real and proper.
Basically, don't offend the reader's senses. Do nothing that jars them out of the story. Keep your facts accurate and your logic sensible (even if your plot and your scenes are fantastic and outlandish), and the reader will follow you through the weirdest stuff. read your dialogue out loud, so that it sounds like human beings and not awful buxom-book stilted dialogue.
Yanno. Easy stuff like that.