Introduction
Introducing Characters, Places, and Setting the Scenes for later. In a mystery
story, this where the characters meet, you would introduce the lead investigator
(like Miss Marple or someone), and perhaps commit the murder. (waggle eyebrows)
This is where you grip your audience and make them want to keep turning the
page. If you don't properly setup everything here, you've lost the mood for
the rest of the story.
Main Event
The 'meat and potatoes' of the story. If this was a murder mystery this is where
the investigation and adventure begins. What you should ask yourself is the
following type of questions (as appropriate):
What is the problem/conflict you are writing about?
What is at stake in the conflict?
Who are the main contestants of this conflict?
What are those characters' weaknesses and strengths?
What is the climax?
How many times have you built suspense into this part of the story?
What is the outcome of the conflict?
If you can answer all these questions, you have everything plotted out well enough now to go for the coup de grace, the final last bit to leave the reader going "Wow! Good book! I'll get her/his next one!"
The Conclusion
This ties up all those loose ends (unless you are purposefully leaving a ton
dangling for the next story, like JKR does, especially in Book Four). In a murder
mystery, the murder is solved, the bad guy goes to jail and the hero/ine heads
off unsuspectingly toward another crime/murder a little wiser and more experienced.
The idea behind the outline is to make sure you have everything linked right so that it flows just the way you want it. Yeah, maybe the readers will guess the murderer because it's obvious. That's what beta readers and pre-readers are for. If they catch on in the fifth chapter of a twenty chapter book, go back to that outline and maybe throw in some twists and turns to make them rethink or heck make that murderer a red herring (see the movie Clue for details *grin*) and have the clues lead to two suspects, one fake and one real. It's all a matter of details and how you lead the reader along with them in the Main Event.