The outline lets you make a roadmap that helps you complete the telling of your story. Typically the story line is one thing, and the steps in telling it are another.

If you are thinking of creating something to sell, agents and editors look for a plotline they know is popular. That is usually something like this: Your protagonist has a problem and in attempting to solve it, gets deeper and deeper in trouble, usually having three catastrophic events and then the solution.

So your outline would say, here is my protagonist. Here is the problem. Here is the first catastrophe, the second, the third and finally the escape from it all. As an example.

Having done three NaNoWriMos I can’t answer your question, because I have never done an outline.

For my last NaNovel I didn’t even a story idea, only a title.

I think what I want to say is that I found that the story writes itself, outline or not.

I’ve done nano… six times. The first year I went without an outline, but since that learning experience I use the snowflake method.

http://www.advancedfictionwriting.com/art/snowflake.php

You don’t have to follow it all the way though, but it’s a great test as to if you have an idea to make a novel out of!

Nano is about having fun – so outline optional, but you can also check out “No Plot? No Problem!” – which is a writing book written by the inventor of Nanowrimo.

It depends on how you write.
For the first NaNo I did, I had a general idea what I wanted to tell, and how it was going to end. I strayed away from the end when I wrote it, though.

The second time, last year, I realized too late that it was NaNo time, and didn’t have an outline or story idea whatsoever.
This year, I do have a general outline again. But an outline is just a general roadmap. I cannot write when I have everything mapped out, I feel crammed and blocked then. But that’s just the way I write.

What helped me over the years is a “lesson” by Kelley Armstrong. She wrote the first part in a way that it can be used for NaNo, but you can use it for any story really.

http://www.kelleyarmstrong.com/cgi-bin/ikonboard.cgi?act=ST;f=17;t=21578

[sorry for any spelling mistakes and/or grammatical errors, English isn’t my native language]

The better question might be “why” not “how.” One of the unique aspects of NaNoWriMo is how it releases your spontaneity by forcing you to turn off the internal editor and just pour out the words for a sustained period—30 very full days. You might discover that having an outline is confining. Many of us treat this as an opportunity to toss out the roadmaps we are so attached to and “just do it.”

I admit, it is rather scary going on a writing trip with no predetermined destination, but that can be half the fun. Why not ditch the outline? Let your creativity take the lead and turn November into totally right side of the brain event.

I consider my outline a high-level set of notes of my proposed novel. It usually ends up like this:

Rebel ship captured by Vader’s ship.
Droids escape to planet.
Luke encounters droids.
Droid runs off, Luke chases. Meets Kenobi.
Luke & Kenobi leave planet.
Find Death Star.

You see, it contains few specifics (unless I add them as notes when I have “great ideas”). Then, I let the outline simmer on the back burner of my mind for awhile. When I think of ways to improve the story, I add them. If a sequence of events doesn’t work, I’ll change it or remove it.

An outline also gives you a heads-up for what abilities your characters will need, which allows you to come up with a backstory for how they acquired those abilities. For example, if your hero needs to pick a lock, maybe it’s because his mean uncle used to lock him up in his room, and he learned to escape.

An outline still allows for a lot of creativity, while providing a framework to keep you on track. And hey, if the story goes a different way, you can always ditch the outline.

This might be helpful:
http://www.advancedfictionwriting.com/art/snowflake.php
Cheers!