For many of us fiction writers, it's important to do research. If you're writing historical fiction, this is particularly true, but even contemporary fiction requires research.
Some of us, however, spend so much time researching, we never finish our novel or even short stories. We feel that we have to get every detail exactly right. While it's important to have your facts correct, it's also important to remember that the story is what's important. More than research and fact checking, you need a good believable story, with well developed characters and a strong plot. The research helps to make your story believable, but there is a time to stop researching and a time to start writing.
If you're wondering if a piece of research should be included in your story, ask yourself these questions: 1) Does the information move the story forward. 2) Can I introduce the information in another manner, e.g. characters who could convey what's important? While you may do hours of research, only include the 1% which actually has something to do with your story.
Try not to use your research as a way to put off the real work - actually writing your story. Research can be another way to procrastinate. Instead, find the necessary information, organize it, and get started writing. If you find you're missing something once you do start writing, bookmark that section, and go back to it later when you're editing and revising.
Finally, keep in mind that all your sources are not the same. Actually going to a courthouse and watching a trial is a lot more beneficial to your research than watching a show on T.V. or reading another author's version in a book. Go to a hospital, or interview your own doctor if you are interested in writing about someone in the medical profession. Talk to people who actually do the job of fireman, lawyer or police officer if these characters are in your book. Are you writing about young people? Observe them at parks, malls, and libraries.
Research is important; it will help you to write a believable story. However, don't use it as a crutch. Happy writing.