For my NaNoWriMo novel I've written a series overview (I actually outlined three books, and the one I'll be writing is the first) with a one-page synopsis for each novel and a ton of handwritten notes when I was structuring the idea. The overview, the synopsis for the first book and my notes are the first additions to my novel notebook. Now I have to work out my timeline and my chapter summaries, which will be today and tomorrow because I'm running out of October.
How (or if) you outline your book is up to you, and if you're interested in trying some new methods there are a lot of resources on the internet that can help. Before I start throwing links at you, let's talk about the good and bad of outlining, and how you can make it work for you.
My first advice on outlining is not to worry about form or format at all. Remember all those rules your English teacher hammered into your head? Toss that right out the window. When it comes to outlining for yourself form doesn't matter, and neither does format. No rulers will be employed, and you will not be graded on how perfect your indentations and margins turn out.
A workable novel outline is like a map of your book. Look at any real map and you'll notice a few things: a generally defined area, natural features, landmarks, communities and the routes you can take to move through the area. A map defines any place it charts in the simplest terms, and features only the information that is necessary for the traveler. What you generally won't see on the map is every single trailer park, bike path, apple tree, chicken place or convenience store in the area, and this is because you don't need that kind of detail to plan a journey. Plus you will discover all those things as you travel, which is kind of the point of any journey through a new place.
It's the same thing with writing an outline for a story. Pretend for a minute that you're the map maker, and the story is the place through which your characters will be traveling. What are the things you need to know in advance in order to make this trip? You'll need to define this, and once you do that's what you put in your outline to create your story map. If you're not sure where to start with what you need, try the reason the story is happening.
I think people are the most interesting part of any story, which is why I usually start developing a story by defining who a character is, what the character wants, and determining what is the worst thing that can happen to them. Example: a vampire-hating psychic thief searches for the vampire who killed her parents, and ends up rescuing and then falling in love with another vampire (and if you've read my novel Night Lost, you also know the big twist at the end with all that.) That was where I started my story map with that idea: the thief, what she wanted, and the worst thing that could happen to her.
You don't have to start your outline with a character, their goals or their conflicts; you can work from any catalyst around which you want to build your story. Some writers use an event, a setting or even an object as their core concept. In Pride and Prejudice Jane Austen used the endless amiable and eligible Mr. Bingley moving into the neighborhood to stir things up for the Bennets. Shirley Jackson used things like lotteries and haunted houses; Tolkien had that ring. It can really be anything, as long as it's compelling enough to have you write an entire book about it.
Outlining works best when it gives you just enough direction to make the journey possible. Again, this is something you have to define. My advice is to keep it as simple as possible, and don't try to nail down every single detail. You'll have plenty of time for that as you do the writing. Keeping it basic will also help because something you've loosely sketched is a lot easier to modify (versus some enormously complicated masterpiece you've chiseled in stone.)
For more ideas and ways to outline your story, check out these links:
Planning, Scheming, and Plotting by Stephannie Beman -- Stephannie talks about her method of sketching out a nice, brief checklist to loosely organize her stories in advance of the writing.
Keith Cronin abstains from Roman numerals in his hybrid pantser-plotter approach to outlining, The Big O.
For those who prefer to write the classic synopsis as an outline -- there are one or two of you like that, yes? -- Charlotte Dillon has a fabulous page of info and links here.
If you'd like to organize your outline online, I recommend trying Hiveword, Mike Fleming's free online novel writing organizer, which I demo'd and reviewed here.
If you hate the idea of outlining at all, you may get some comfort (and ideas) from Crawford Kilian's post Writing Without an Outline.
Advice from a master: Effectively Outlining Your Plot by Lee Masterson
Alicia Rasley's classic article Outline Your Novel in Thirty Minutes asks all the right questions; you provide the answers.
For a very brief outline, test drive my one-page ten point novel concept outline template (the first page is the blank template; the second is filled in as an example.)
If you like Randy Ingermanson's Snowflake Method of outlining, you'll probably also love TextTree, a freeware written as a companion program for it.
TiddlyWiki is a free service that provides a reusable non-linear personal web notebook (LJ Cohen did a terrific virtual workshop a few years back on how to use TiddlyWiki to organize your novel.)
Try virtual whiteboarding with the free online service Trello, which I demo'd and reviewed here.
Juliette Wade's Sequence Outlining offers an event-driven method of outlining.
Writing.com has a Blank Novel Outline worksheet here.
And finally, a post I wrote that after five years remains the #1 most popular on PBW, my Novel Outlining 101.