Characters are tricky creatures. Too much detail given in one blob can make them look like a grocery list of traits. Something mentioned too late into the book can throw the reader off the page. I tend to relatively light description because, as a reader, I like to imagine characters that appeal to me. A few key physical traits will allow me to envision what I want to see.
Character background, though, is a bit more complex. Background will influence how a character reacts to a current situation. To me, characters are mostly about attitudes, for good or bad. My character sections are about who they are, and less about how they look.
The 'how they look' section is the one that is most likely to change during the story. For instance, this is a great place to jot down when the character gets a new scar on his right arm so that you can easily check the location later.
If you choose to use one of the novel templates for Scrivener, the program provides a nice, simple character template that lets you get the basics down and you can add anything more to it that you like. It also has a template for places, which is always handy to remember (for instance) what the view was outside the window and what color the walls were in the bedroom. Or you can use it for entire cities and worlds to get as much of the basics down as possible.
When I start notes on a new story, I rarely have names. I usually use C1, C2, etc. By the time I get to putting the material into order, I look for names. Sometimes even those names don't stick. Other times, the name comes right with the first view of the character.
(Novel titles are the same. Either one comes with the idea, or else I play around with stuff until something sticks. Titles have changed all the way to the final draft.)
Any of these sections can grow both during the outline phase and during the actual writing. Add to them. Change things. Make improvements. That's why you do notes -- not to set something in stone, but rather to have a starting place and some basics to consider, and so that you can keep everything straight.
Now, let's talk about outlines.
People often find even the idea of outlines annoying. Those people lose interest in the story once they've written the idea out, even in a short set of notes. (Some of the same people have trouble with editing; once they've told the story, they lose interest in it.) I am not one of these people. If I have a story to tell, working on the outline is barely scratching the surface and certainly doesn't give me the character reactions, dialog, etc., that is the true story.
Outlines come in many different styles. Some are simply a line or two per chapter (or scene) that reminds you of what you want to cover in this section. Others are more complex and become a small synopsis of the section you're about to write.
Some people have very good luck with writing part of the story, then doing a few notecards to cover the next few steps. After they write those steps out, they outline a little farther into the story. This way, they can see the next sections based on what has happened and what they've written closely influences what happens next.
My outlines are sometimes a simple list of chapters and events and other times are long lists of steps for each chapter, which might include motivations, a bit of dialog that came to me and I don't want to forget, and any other bits and pieces I drop in.
I can work out the basic story problems in an outline and fix things far easier there than in an already written book. It's easier to drop in little hints earlier in the outline when you suddenly realize there is something big about to happen and you don't want it to come completely out of nowhere. It's far easier to move things around and add in new characters and subplots in an outline than in an already finished first draft.
And they are excellent for NaNo.
So here is the last part of this rambling set of material which brings up back to NaNo -- which is now less than 3 months away. I almost always use outlines for NaNo. They are often extensive ones and I divide them up into chapters, and each entry is (in general) equal to a certain number of words. Let's say I want to write 50k for NaNo. If I have 100 entries on my outline, each one has to equal 500 words worth of written material in the story. The more entries, the fewer words per outline point. At 200 entries, you only have to write 250 words for each of those points. That really isn't a difficult amount to write if you have some idea of what you want to cover. Every time you come up with a basic idea for a scene break it down into at least three pieces of before, during and after. Let's say someone walks in on an argument:
Before -- why the person is here, what the person sees that might be clues to trouble ahead. (Subtle would be the car belonging to sister's boyfriend. Obvious would be things knocked over and broken.)
During -- steps into room and finds two angry people. What are they yelling about? What do they look like? What does the person who stepped in do?
After -- once fight breaks up (whether through intervention or one of them walking out), what happens? Can they hear squealing tires of car? Does sister go to her room and lock the door, refusing to talk about it? Is it left to person who walked in to make things look right before parents get home?
Those are pretty obvious things. If you listed the scene as 'arrives to find sister and her boyfriend fighting' that should be an easy 500 words. However, if you break the scene down into smaller pieces, you can often get far more out of it. Watch for places to add description and senses.
And if you get stuck, ask this question: What is the worst thing that could happen right now?
That doesn't mean end-of-the-world crisis. Lost house keys could be a problem with unhappy kids in the car. A rainstorm could ruin a picnic. Late for school, late for work, forgot a birthday -- even little things can generate conflict.
Novels are all about conflict. If your characters are simply gliding along the path of happiness, most of the time that will make a boring story. I won't say all the time -- there are always cases where someone writes something so well that they overcome the limitations.
So write what calls to you. Remember you are working on a first draft. Expect to have to rework it and don't pretend otherwise. That way you won't be disappointed and you will start to think and work like a professional.