Make your question concise and articulate. You don’t ask “Tell me everything you know about glass manufacture in the seventeenth century”; you ask – as I did for one of the Musketeer Mysteries, “How big a mirror would a middle class woman in seventeenth century France own? And would it be glass or polished metal?”
(It is, however, a bad idea to call your local police and ask: “If you have a corpse, massing around 150lbs, where would you hide it in the metro area so it’s never found?” Another novice writer who was part of my group 15 years ago did that. The police did let her go after two hours.)
Accept that your time is finite, and that you can’t research every detail. Research just enough to write a first draft of your book, and any missing information will be both obvious and accurately pinpointed. Fix any missing information in revision, then hand it to your experts to read for accuracy before the publisher ever sees it.
When you’re done, remember to thank all your human sources of information.
But the most important thing is to know when you’ve researched enough and when to set the research aside and start writing.
You know enough to begin. What you don’t know can always be filled in. The alternative is to spend the rest of your life researching the perfect novel you will never write.
Check out the previous installments in the series: