In an effort to figure out which story to write for NaNoWriMo, I'll go through how the cast of the stories I've detailed before.
First up, Mecha Academy. This story started off inspired by several anime and related RPGs. The idea was to follow a group of cadets through their time at the titular academy. This meant coming up with a squad's worth of characters. One of the cast was an idea I'd been playing with after reading through the Mekton Zeta lifepath generator,* resulting in a young woman whose family had defected to the other side. After mulling things around a bit, I determined that she had gone, too, but returned with some assistance from a spy from her homeland. Dusty, for that's the name she answers to, fills the somber niche in the squad, plus can be a source of internal conflict.
That still left me with four characters. However, with Dusty as a source of conflict, I added someone for her to conflict with. Hence, Rhiannon, the daughter of a duke, and whose brother died when Dusty's family defected. Ta-daa! Instant conflict! But, why is Rhiannon out at a frontier academy instead of one on a core world?** The obvious answer - she wants to make it on her own merit instead of being treated as nobility. On a border world, she thinks that she'd be treated just like every other recruit. This, though, implies that the core academies tend to make it easier for the spawn of nobility to graduate.
So, now with two characters who will generate conflict, what next? Maybe a hint of romance, to attract shippers***. Mind, shipping will happen, no matter what. But, I get to pair off my characters first. Nyaah! :P So, next character was Rick, a hot-shot type with a flair for piloting. All space opera has a hot-shot pilot; it's in the rules somewhere. And, most hot-shot pilots are considered dashing. If Rhiannon wants Rick, she's going to have to get his attention.
The next character is Lars. I needed someone who is local (though Rick could also be from the same world). With Lars, I made him a farm boy, giving the squad some basic survival skills before classes start and a guide to the local area. Rick, though, is more familiar with the main city. Lars is also more physical, the biggest of the team. Trope-wise, he's the Big Guy.
This left me with one more character. The big difficulty here is to avoid adding a character just to fill the role. That would have the character just there for the sake of being there, with no other motivation. I didn't want Miyami to suffer like that. She needed her own storyline. Thus, she's actually underage. Miyami left home to join the military to help her parents out with extra cash. She forged her age and enlisted. This also means she's a hacker, a skill that the other four don't really have. Miyami now has her niche and a secret to keep hidden until she graduates.
Now, I have my squad, some conflict already, potential hookups and shipping. All that's needed is a plot.
In part 2, I'll cover Beaver Flight.
* A series of tables with suggestions for a character's background; the option was to roll or choose. In this case, I opted to choose.
** And you can see elements of setting building up. The setting has been greatly expanded, allowing for nobility, flying cars, and giant mecha.
*** Shipping is the pairing of two characters romantically, usually in fanfiction. Gender doesn't matter. Shippers are those who ship characters.