Let's get to it.
Know What You're Talking About
Nothing is more frustrating than coming across a writer who doesn't know what he/she's talking about, and there's nothing more embarrassing than handing in a work only to realize some small event in your story (which
made complete sense to you) is physically impossible.
I experienced this in a writing workshop, the other day. I submitted a story that tells the stories of five people who survive a plane crash, and described a survivor walking around after having a morphine/vicodin cocktail. This was a big mistake. I should've researched narcotics before putting them in my piece. Turns out that giving yourself a shot of those two would knock you out cold, or kill you. Ouch.
It feels damn good when someone says, "But X doesn't even exist, did you make it up?" and you can respond, "Actually X does. If you look at Y...." Dan Brown does extensive research in his novels. He outright says in the beginning of Deception Point that, "all technologies in this novel are real."
But it's more than that. Researching can help you stumble upon new material, new id eas for future stories are interesting twists to apply to drafts you're sitting down and editing, at the moment. Make sure you're not writing a nonfiction book when you really mean to write fiction, however-know when to stop researching before you forget all about your story!