The Canonical, Stereotypical, Not Necessarily Applicable, Do-It-Yourself Novel Writing Kit
as derived from the comments of various authors including Lester Dent, John Gallishaw, Jack Bickham, Tom Holt and Terry Pratchett
So You Want To Write A Novel?
Here's how to do it in three E-Z steps.
Formulate a thought as to what the story might be about and write it down.
...and so on, until you get a feeling as to whether there's enough to the idea such that you can get 50,000 words out of it. If not, throw what you've got so far into the parts bin for later; no point in wasting all that thought.
You could use a theme ("Love Conquers All", that sort of thing) to unpack the idea; if the idea was a theme you could throw in another ("Death Before Dishonor") and use that.
Assuming you've gotten this far, with the specifics obtained you can decide on what type of characters might be involved -- obvious classifications being Hero, Romantic Interest, and Villain; you'll want something more specific. It won't hurt to have a large cast since you can always remove them again.
Philip K Dick suggested that one character is going to benefit from the idea and one is going to be harmed by it; hero or villain is up to you.
With characters involved you can get some ideas as to what sort of fates they merit...and at this point you can move on to --
There's a big difference between the essayist's outline — I - II - III / A - B - C — and the artist's outline, which is what I mean by cartoon. You're a novelist; you almost certainly want the latter. This method simply requires that you (arbitrarily) create pieces of the story at key places throughout its structure: e.g. a few sentences of the beginning, a paragraph's worth of the middle, a few more sentences of the end.
Having done this you can create additional sections by interpolation, which in turn can be used to create even more -- all of them presumably requiring earlier or later developments, additional characters, incidental objects that need acquiring, and so on. (This is where story and character arcs come in, since an arc is essentially two endpoints, a lot of interpolation, and a point of maximum deviation. Beginning, End, Middle.)
At some point you'll either give up in disgust or think "This'll do". If you can think of what the back cover blurb will say, you're probably ready to move along to --
Apparently it's time to turn the cartoon into a portrait by filling it out, section by section. In Approximately Five Steps a section "should" (ha!) run as follows:
Who, what, where, when -- choose one or more.
Typically, show a character's wish to maintain or change the status quo (the character is threatened or declares a desire).
Given the structure above, the character would take the beyond-present-character decision (optionally combining it with the prop from 3a) and act toward resolution.
Show the effects on the character -- towards the beginning, this typically means Things Get Worse -- and lead into the next scene.
Canonically-Stereotypically, a scene "should" (ha!) run about 800 words (note that this is 3.2 standard manuscript pages, thereby avoiding Intimidating Blank Page Syndrome when it comes time to start the next scene), which means you'll need 63 of them for your Canonical Stereotypical Novel.
A.E. Van Vogt favored putting an unexpected plot twist in every scene; some people took this to mean putting in a Brand New Unusual Idea in every scene, which is a nice touch if you can manage it. If not, most likely no one will notice.
That's about it. Good luck...and don't forget to ignore everything you've just read when it suits you.