So you've got a great idea, and you're going to dedicate yourself to getting this book done. Congrats! So what structure is your story going to take? How fast paced is your story?
These are things that people typically don't think about consciously, but the actual structuring of your story is one that you should spend some time on. What POV are you in-first or third? How many characters are you following, and how deep into their thoughts are you willing to go? How soon do you launch into your main plot, or introduce us to the conflict? Even seat of the pants writers should have some idea of these things, either before they start or soon after starting.
Deciding these things is often a delicate balancing act, and the more you write the more the experience will benefit you. Unfortunately, the experience of writing an entire book is the only thing that will prepare you for writing the next one, and the next, and then maybe, finally the one that will actually be good enough to publish. Pacing and execution are not easy, and can break an otherwise fantastic story.
First, the structure. Try to decide early on how many main characters you have and the best POV to take, or consider it as you write. There are several ways to tell a story, but some are better for certain types of stories than others, and only you can decide what is best for yours.
Are you following one person or many? Does the villain in your story get a say in anything? How will all of these POVs interact, and how does each one actually advance the story?
There are a few traps here to avoid. Don't write from a character's POV if they don't actually have an important role. Not only will it slow your story down, but people will resent the character. Also, if your story is only going to follow one person in a limited third person POV or from first person, make sure to make them very interesting characters and have them develop throughout the story, or your readers may start getting bored. If you're writing from an omniscient narrator's perspective, make sure it's clear who the lens is focused on at the moment. Head hopping without a clear indication of when it occurs (like with a chapter break) will do nothing but confuse your readers.
Secondly, we have pacing. How soon does the important part of your story begin? How long do you spend setting it up?
I would recommend not taking too long to introduce the main conflict. Have an idea of what the conflict is early on, and don't try to keep main plot points in suspense when they don't matter that much to the overall plot. I made that mistake in my first novel-I wrote thirty thousand words to introduce a plot point that was taken for granted in the grand scheme of the story. If the plot point you're trying to keep mysterious and spending a lot of time on is something that would ordinarily show up on the plot description on the back of the book, don't bother spending so many words on it. Introducing it earlier will make your book more exciting and save you editing later.
On the flipside, of course, don't rush into conflict so quickly that you sacrifice everything else. If your character is rushing out of the inn he works at to follow some mysterious wizard, that sounds like a great plot introduction-unless it's happening on page two, in which case I'm not sure I care about him enough yet to want to continue.
Make sure everything you write matters to the story. This is basically just avoiding filler. Every scene should advance something that is important to the story you are writing or the world you are building. Don't waste time on details that don't matter; people don't really care what your main character had for breakfast.
Of course, don't skip things that are necessary, either. If your character was gravely injured in a fight, don't make him recover after a day just to keep the story moving. Keep things fast paced, but keep them realistic as well. If you aren't writing an action scene, use the space to develop the character. The order things should be addressed in terms of importance, especially after the story has begun, should be plot advancement, character advancement, and finally worldbuilding. If the scene you're writing is not addressing any of those things, think about it further before writing it.
To sum up, pacing and structuring your story is vastly important. It's also the hardest thing to learn and the hardest to teach, because it is so dependent on experience and on the exact story you are writing. The best thing to do, especially when you are uncertain, is to write far more than you think you need. If you're not sure if you want an extra character POV, write them both and decide later based on what you've written. It is easier to delete than to add. This also makes editing easier, which is what I will talk about next time.