If there is one thing I'm reminded of when writing, it's how I must learn to keep notes along the way. My recent WIP, which I've finally finished, gave me reason to think about this organization thing a little more carefully. When including the ages of my older characters and the mention of past events in which they were included, I realized there was a discrepancy. I had to go back and search for each point in the story where information had to be changed so that all would make sense. A timeline would have helped to prevent that mistake and spending valuable time undoing the errors.
I feel there is definitely the need for a timeline. If you are going to include a story setting that expands several days, several weeks, or several years, it doesn't matter. Create a timeline to fill out along the way as you write. Dates, ages, duration of time, all can be thrown out of kilter if you don't keep track. If you are a computer guru who enjoys software with all its colors and gizmo devices to create your timeline, check out TIMEGLIDER . The software is free and it will give you choices for how you would like your timeline to look and then store it for you.
Another point in story writing which can be a challenge and thus cause for error involves character interactions --- who said what to whom and where they were, where they've been, how to get there from here---well, you get the picture. Or maybe you don't. One of the teaching strategies I've learned is mind mapping. It truly works. I've seen this used with various mediums, including one lady's suggestion to create a map or miniature model of the town in which your story takes place. Mapping can be a great tool and will visualize any information you like. Another free site/software that uses mapping tools is MINDMEISTER . Once you've signed up, you can create a map webbing for your characters, locations of places in which they live or visit, events, etc.
Of course, if you are more of the paper and pencil type, you can always jot your timeline down on paper. However, I can't emphasize enough how important it is to add to it as you write. Perhaps at the end of each writing session, or after each chapter you've written would work. I know how difficult this may be when you're in the writing zone, that mad frenzy of passion where your fingers are burning up the keyboard as the words pour out. And you're supposed to stop and take a moment to jot down notes? Not easy, but find a point where you can do so. As for mapping without computer software, you might try note cards. Plaster them on the wall of your writing space or spread out on the floor, or wherever you can.
I think these tools work. Try out different methods and find the one that fits you. Then use it. That way when you get to that point in the story where you think, "Did I say Martha was five when that happened?" or "Did Martha tell Tim she was in love with him before or after she dumped Tom?", you can look at your timeline or map for the answers within seconds, rather than spending extra time going back through your novel to find out.
Writing should be fun, but the organization helps in the editing process. And at the very least it will save you time for, well, for all the other important things in your life that you've neglected while--what else?--WRITING!