As a published mystery writer, I only have one piece of advice for you. Write about what you know about. If you don't know about crime, criminals and firearms, perhaps you should select a topic you are more familar with.
Research is better, when you live it, like the likes of Jack London, or Ernest Hemingway. Most people that write usually have one or two good books in them. That's because their life experiences have been limited. I've had some favorite authors, but most of their books are more or less fomula, and over time I've discarded them. People that base their work on research sooner or later, get something wrong. It's like a Professor that went from college to teaching. Everything he knows comes from books. No life experience to know if who ever wrote the book knew what he was talking about. I loved teachers who worked in their field. They brought a lot to the classroom when they could tell you what parts of the textbook you could discard as ****.
