It's fairly simple for things to get complicated when writing a longer piece, such as a novel or novelette. As I edit one book for what feels like the thousandth time, I still notice discrepancies in eye/hair color, character activity and timing. You will too.
In these days of too-few editors (and too-many unedited novels online), it's important to take pride in your work and assume responsibility for accuracy and consistency. You can't really trust a Beta reader (helpful eyes) or editor to find it all. Nor should you. This is your book, and only you know who is supposed to do, say and think what. Editors are wonderful, but also human. You still want to check with a read-through.
So how do you do it? Here are some recommendations:
1. Keep an index card file, noting each character's physical appearance, job, background, likes/dislikes, aspirations and anything else that seems relevant. This is also a way to get to really know your character. Refer to the cards whenever you're writing about someone after a bit of time away. Cards are also good for setting scenes, for example town descriptions, landmarks. List minor characters to the extent that you're using them.
2. Do a timeline. It is incredibly easy to lose track of events in time, allowing too few days or weeks to pass from one event to another, or mixing up a scene in time. I recommend listing each scene—yes, every one of them—on a card with the basic event that's occurring and the time.
3. Lay them straight. Use your cards to discover needed changes in the order of events. I took one editor's advice and laid the scene cards out on a tabletop. It's a good way to find out where you may have jumped the gun on an event or scene, or to decide better locations for a scene.
4. Read it out loud. There is nothing like the spoken voice for pointing out awkward dialogue or prose. I find it a key way to determine where better punctuation will help, where I've repeated words and weakened a sentence (you can also do a word check to find this out—it can be shocking how much one repeats favorite words). Mistakes will pop out in front of you.
5. Look it up. Everyone has grammar monsters, those unsure structures that haunt you every time you come across them. Underline areas you're not sure of. Look them up in other writer's works, in grammar guides like "Eats, Shoots & Leaves," "The Chicago Manual of Style," "The Writer's Digest Grammar Desk Reference" or dozens of other grammar guides on your library shelves.
Finally, do not—as the saying goes—throw the baby out with the bathwater. If what you have written has flare and style, spirit and rhythm, then preserve that. Overediting sometimes stiffens and diminishes your writing. Guard against that by, again, reading changes out loud.
Ann Connery Frantz writes "Read It and Reap," a column for book clubs in the Telegram & Gazette, and is a founding member of the Seven Bridge Writers Collaborative.