But research can cause problems for writers.
1. When to do it.
If you start doing lots of research before you begin writing your story you may end up researching things you don't actually need in the end. You may have decided to set your story in Paris, for example, and duly set off to France for a spot of authenticity (it's a hard life, but someone's got to do it...) but in the course of writing you realise that actually the story works better set in a crofter's cott in the Hebrides. I think it's best to have a rough draft of the story already on the page before you start doing extensive research because then you'll know which areas to focus on.
2. Displacement activity
Another reason to save as much research as you can until after you've got a rough draft down is that research is simply the best displacement activity ever. You can easily justify a day spent researching something, compared to a day watching America's Next Top Model. You may scoff at my choice of example but the truth is that the outcome, in terms of words on the page, is exactly the same: Nil. I've known people spend years on research for their still unwritten story. That's not a problem of course if that's how they want to work and they don't have any time schedule in mind, but I think most people hope to be more productive.
3. Talking too much
Research often involves talking to interesting people about what they do. This is a treat, but it has the drawback that you end up telling people about what you're working on. The problem here is that if you talk about a project a lot it tends to lose a little impetus. Talk too much about it and the desire to communicate to the reader might dissipate.
4. Knowing too much.
When I was working on Kissing Mr Wrong I got an editorial note that was short but to the point: Too many cemeteries. The trouble was, I'd been on a research trip to the Somme and been intensely moved by the war cemeteries. I'd written it all up in great detail and taken thousands of photos, and I wanted to share the experience. But a novel isn't really the place for that. Yes, a bit of detail works, but if the reader wanted to know about the war cemeteries and memorials they'd read a history book. My editor was right - there were too many cemeteries in the novel and they had to go. (I have to admit that's been the hardest edit I've had to do emotionally as I was - am - passionate about them, although technically it wasn't too difficult.)
Don't get me wrong - I love research and sometimes you can't write anything until you've done some. Just, I think it's best to avoid getting to caught up in the research to the exclusion of the writing.