First Plot Point
This is sometimes called the point of no return. This is the first step taken toward the climax of the story. Your characters get off their collective butts and do something. Maybe they're reluctant, maybe they're eager, but they have a goal and they're heading toward it.
I say that because of how often I want to take a cattle prod to characters in something I'm reading. Yes, this includes professionally published books. I do not understand the fascination with characters who refuse to do anything or to take any initiative.
As mentioned in yesterday's post, the conflict needs to be genuine and serious. It also needs to be
clear to the reader -- in that there is a conflict. Mysterious
antagonists with unknown plots are all well and good, but it does need
to be clear that something is afoot and the characters are going to do
something about it.
Sub-plots are a common
feature in books, whether they're things that must be done before
addressing the major problem or parallel plotlines involving minor
characters and other challenges. The short answer on what to do with
them is: write a full plot sketch for each one, with all of the steps,
and work them into the main plotline. A scene that's an Other Plot Point
for the main plot may also be the Climax of a secondary plot.
The story might begin at the first plot point. Or maybe at the inciting incident. TV writers have developed a habit, recently, of starting just before the climax and then flashing back to tell the beginning of the story -- I hate this. I hated it when Lovecraft told me the end of the story first, too. Then again, Lovecraft's stories all end pretty much the same.
It's a question of how much you will need to explain to the reader in exchange for beginning at a dramatic moment. Exposition is a whole 'nother series of posts, though.