After the request for writing tips from last week's comment section, I went back and reread my Writing Tips posts (mostly found in October 2009) to refresh my memory about what I'd already covered. I wish I had a treasure chest of secrets to share with you because I certainly would, but I can only come up with a couple of things to add to what I already wrote.
Keep in mind I'm the Accidental Writer and may not be the best source for these types of things...but I'll still try to help, and I'll still share what I can.
For starters, it didn't look like I'd addressed theme in the previous Writing Tips posts, and theme is very important. It's like the framework and invisible substrate which is then artfully concealed by the drywall and stucco and architectural detail of your story. For a story--especially a mystery--to hold together, the hidden stuff has to be really strong, and what helps strengthen any story is a defined theme.
I like when I have a theme from the get-go. Something I what to say or explore or present to my reader as food for thought. The theme is what I'm passionate about. It's the purpose for taking a year or more out of my life to tell a story. All my books have a theme. Some are stronger (or more obvious) than others, but they all have one. For example, in Sammy Keyes and the Runaway Elf, the theme was forgiveness--the power of, the benefit of, and the cost of bitterly resisting.
Now, I've found that the trick to making your theme work powerfully is to give it some backup. Subplots are great for this. (I feel like I've already talked about this, but maybe I've just talked about it at schools during workshop presentations, not here. So I'll just go on like I haven't typed about it. Forgive me if this is a boring redundancy.)
Anyway, subplots. In most Sammy mysteries you'll find three threads--the mystery, Sammy's home life, and Sammy's school life. Most people say the mystery is the main plot and the other two are subplots, but I sort of view them as all vying for that #1 position.
To me subplots are as important as the main plot. They're like the backup singers who are sometimes better than the star singer. (For example Merry Clayton--whom you've never heard of--kicks Mick Jagger's tush in Gimme Shelter...and Mick lets her, which makes the whole thing work fabulously.) And for the subplots to contribute to their full potential, they must be in harmony with the theme. So in Runaway Elf, the motivation behind the actions of each subplot's main characters is found within the theme--forgiveness.
Subplots will save you. When you're stuck in your plotting, when you're sagging in your novel's middle, subplots will save you. I believe if your novel is sagging it's because your character needs a job. Or a dog. Or a scary neighbor. Mess with their lives a little more. If your protagonist's life is too linear (or too smooth or becoming boring), add a thread. But then follow that thread through to the end! Don't leave us dangling with your little subplots to nowhere! And ideally, when you tie up all your subplots they should each contribute to the story as a whole...which means that--if at all possible--they should somehow hearken back to the theme.
I wish I had something to show you. Some visual to illustrate my process, but I don't. Partly because I don't think of it as being worthy of sharing. I do what I do, and with each book I'm re-amazed that it all turned out well. It always feels like an accident, even though I know it's not (entirely). I always feel a little like a fraud, even though at nearly 30 books, I know I'm doing something right. And it's somewhat comforting to know that this is apparently universal with writers. I've learned from reading what other writers say about themselves, that we're all a bit bemused by how we do what we do. At least the writers I like are. And I think that's partly because we dive in and hold our breath, hoping, praying we can swim well enough to make it to The End.
It's also because my outlines consist of crude diagrams, random words, and cryptic notes about possible events. Just enough to remind my brain what it was thinking. I don't have a chapter-by-chapter outline. Half the time I don't know who's going to answer the door Sammy's just knocked on. But I do know that whoever answers had better support the theme or I'll slam the door on them and knock again.
Has this been at all helpful? There are probably hundreds of books on writing. Maybe thousands! You can read them all and still feel unprepared. So stop. If you've got the basics of your story down, if you've got a theme, some subplots and an ending in mind, it's time to quit reading books about writing and start writing.