This goes for non-fiction and fiction. It goes without saying that the facts in your non-fiction writing must be accurate. The “truth” is the very definition of non-fiction.
When writing fiction, your story line doesn’t need to be factual. However, you’ll increase the credibility of your writing if you have the facts correct about the setting, the objects used in the piece, and about the history of the area.
Areas where you need facts are:
1. If you’re using a real city as your location, your facts about that city need to be accurate. Your readers will catch your errors. For example, don’t put the bakery on the wrong corner or put in a park that doesn’t exist.
2. History. If you bring up facts from the history of the setting, your facts need to be correct.
3. People. If you talk about local people to add flavor to your book, the facts about them need to be accurate.
4. Props. You need to research information about the props used in the story and how they work. For example, make sure you don’t call a gun by the wrong name or if your main character uses a tool for his profession, make sure you have your information correct.
Attention to detail will always help your writing.