Sometimes, though, you may feel that what you need can't be found in a book. For example, one of the characters in your book is a police officer, but you, personally, know nothing or very little about being an officer or following police procedures. If you have time, you can probably find a class on police procedure at your local college or junior college. You might also know someone who works for your local police department who can help you with information or an answer to a question.
Before you do that, though, do some research. The police or contact person with the police can't give you the answer you want unless you know what you want. You're going to have to narrow down your question. Rather than asking how police investigate a crime scene, try to narrow it down to specifically what you need to know.
To narrow down your question, you can turn to books. For example, I have a textbook called Practical Homicide Investigation: Tactics, Procedures and Forensic Techniques. It's the second edition and it's pretty old (1993), but I still check it first for the basics.
For most subjects, it's fairly easy to do research. And sometimes you can ask experts, either in person on online.
For example, there's a guy online who can be a good source: Lee Lofland -- He has a Writer's Digest book called Police Procedure & Investigation. You can also check out his blog, The Graveyard Shift.
You may be thinking that you don't really need to do the research because your editor will catch any mistakes. Unless your editor is an expert in police procedure -- or whatever your topic is -- she probably won't catch it. There are plenty of things that your editor will catch, from spelling to commas to punctuation to characters who change names mid-book to the overall story line. Unless you hire and pay an editor or researcher to do the work, it's up to you. Even if you can afford to do that, though, it's good for you to know as much as you can about the topic or job or setting.
Helen Ginger is an author, blogger, and the Coordinator of Story Circle Network's Editorial Services and writing coach. She teaches public speaking as well as writing and marketing workshops. In addition, her free ezine, Doing It Write, which goes out to subscribers around the globe, is now in its fourteenth year of publication. You can follow Helen on Twitter or connect with her on Facebook and LinkedIn. Helen is the author of 3 books in TSTC Publishing’s TechCareers series, Angel Sometimes, and two of her short stories can be found in the anthology, The Corner Cafe. Her next book, Dismembering the Past, is due out in Spring 2013.