Okay, I recommend following this map of the Six Layers. If you build from the core out, you get solid storytelling.
How to write from the core out:
If you throw in random crap at the last minute, you get modern entertainment. But it's NaNoWriMo: Write badly with pride! There's nothing wrong with fooling around just for the fun of it. If you're ever going to do it, NaNoWriMo is a great time.
Writing by the seat of your pants:
Steps 1-2 are transposable. For NaNoWriMo, you have chosen to start with #2 Form (a novel) which is fine.
Let's do this thing!
Spend way too much money here:
Now you need #1 Idea. Themes can fall into this category. Simple themes are just the topic: Love, Hope, Nature, Death, etc. At that level you can present multiple perspectives on the same thing. Frex, Damask is fundamentally about Identity, but each headmate handles their situation very differently. Another option is to pair opposites: Darkness and Light, Man vs. Nature, etc. More often, the theme is a thesis -- the author says something about the topic. Love Is Great, Love Sucks, Do Not Go Gently Into That Good Night, Trust No One -- these are all thesis types of theme. I bailed out of Agents of SHIELD because Power Always Corrupts puts me in a fucking awful mood. >_<
Pick one to three themes you care about: either multiple theses around one topic, several unrelated theses, or a binary pair. Is there anything you think the world really needs more of? A topic you've been itching to tackle? Something you want to convince people is true? Put it here.
Writing with themes:
These are topics:
Most of these are theses:
Here are some worthy causes:
Can't decide? It's NaNoWriMo! Number a list and roll some dice. You might come up with something really awesome. If you hate the results, you can always try again.
Next comes #3 Idiom. Symbols often go here. They can be foundational flavors. When I say that Terramagne holds a lot of Cinematic and Golden Age style, the capes and masks are symbols which enact those. It's why everyone talks about being a "white cape" or "black cape," and why masks have legal status -- a cape persona can be wiped out in court, like disbanding a company, although far more often it's done via social shunning. The Spectrum was summarily declared Not A Superhero Team by everyone in Easy City, and the rest of the world agreed.
WARNING: Symbolism has some confluence, but also varies *drastically* from one culture to another! Whatever time/place you are writing, make sure you use the right symbol set. If you are worldbuilding from scratch, you are free to make your own. I did this for the alchemy in the Steamsmith and the Six Races (plus dragons) in A Conflagration of Dragons. For me this is as fun as an artist buying a handful of paints just to screw off with on a rainy Saturday. :D It's NaNoWriMo, go nuts.
It's totally okay to write a story as concept art, and this is where you use symbols to do that. Concept art is all about a relatively quick image that conveys the mood and tone of a storyline. It's all about color and shapes and implications. You don't have to put more detail than you want.
Learn about symbols:
These are common literary symbols:
Here are some visual symbols:
#4 is Structure. Symbols rarely go here, but they can be employed to great effect. Frex, Jackie Frost and Fireheart are a diametric team, Fire and Ice. (That's thematic too.) Her symbolism is cold (blue and white, ice skates, etc.) while his is hot (copper, chopping firewood), and together they make steam that makes shit happen. Any set of characteristics you can use to distinguish individuals is symbol used as structure. Astrological signs, classical Greek elements, Feng Shui elements, 9 intelligences, Myers-Briggs, the four seasons -- whatever you like.
Ways to distinguish characters:
#5 Craft is all about your skill and technical finesse, not about the literary trappings. If you're writing a novel, you're about to get a buttload of practice. You may as well pick something you want to get better at and bang out 50,000 words of it.
I spent junior high and high school writing one poem every weekday. When I did the Gray School of Wizardry I was still amazed at how much learning can happen from sheer mass quantity of action, writing 10,000 word classes in batches to lay out the curriculum. When I launched Polychrome Heroics, I whacked out a few dozen character sheets just to get a feel for the kind of people who live in this setting, and again surprised myself with how different they were from mainstream superheros or supervillains. Don't underestimate the power of cramming a lot of action into a short time. You can practice 8-16 hours a day in college. You can write a book in a month.
On practicing a ton:
Some things you might choose to practice:
#6 is Surface. It's what people notice first about your work, but it matters the least. Except for one thing: if you've put symbols deeper down, you can put them here too, and it works like a top coat on paint, lending a high gloss. If you've ever seen an oil painting of the ocean that looks just luminous, that's often how it's done and that's about the effect you get with surface symbolism. It connects to the deeper stuff and pulls people in.
When you write with a fractal structure, it can be any fractal, but you need to pick one that matches your material. Spirals such as the Fibonacci utterly dominate Asian literature, ideal for iterating a single theme. Pythagoras Tree (very one-sided) and Fractal Tree (bilateral symmetry) are two different branching patterns. If you have a main theme and a secondary theme, consider the Mandelbrot (a big blob and a smaller blob). If you have three main ideas, there's the Sierpinski Triangle. For six -- particularly mirrored sets of three -- use the Koch Snowflake. You can draw the fractal and then jot down larger and smaller ideas on its parts. Or you can just do it in your head.
To do this step, use the lists of symbols from #3 Idiom above. In writing from the core out, create a fractal structure in which themes branch into smaller symbols. For example:
Themes: Love & Death
Idiom: The Language of Flowers (colors, meanings, nature)
Surface: Florists, floral fabrics, flower gardens, colors named for flowers, characters with floral names or who wear flowers
Idiom: Goth Culture (introspection, dark ostentatious fashions, cemeteries, cathedrals)
Surface: top hats, burgundy velvet dresses, narrow pointed arches, ravens, funeral marches
Some things cross over, such as color symbolism. Flowers use bright and pastel colors; Goths use dark neutrals and a few jewel tones.
Suppose that you have a nurturing man who runs a florist shop and a fierce Goth chick who buys flowers from him. Those two will have a hard time getting along for the 10 minutes it takes to make a sale, and that's before you have aliens invade the city in Chapter 2. But because you have built those themes and symbols into the whole novel, the story will stand up when slain aliens release carnivorous plants from their graves because they carry symbiotic seeds that only sprout after they die.
You get the idea. Go write something awesome.