I've definitely done the "no outline" approach. When I completed the first draft of my novel, Gateway, I was participating in NaNoWriMo, which is the absolute definition of winging it. I plotted as I went, going with the flow and getting those words down. At the end of it, I certainly felt accomplished--I'd finished draft one of my first novel! I also had a feeling that half of what I'd written was a steaming pile of crap. And it was. Which doesn't mean I'm not profoundly grateful for my NaNoWriMo experience. Half of it might have been crap, but the other half varied from meh to pretty good. The core of the story remained the same in subsequent rewrites, though several plot points changed and became stronger.
I came to realize that I had the same issue with writing my novel that I had with writing screenplays. My characters and dialogue were good, but my plotting, specifically in the middle of my book, needed vast improvement. The beginning and the end were strong, but the middle portion fell flat. There was a raising of stakes, but not enough.
In draft 2 I made lateral moves, changing plot elements, but not necessarily strengthening them. Between the 2nd and 3rd drafts I read some books that really enlightened me. One was Plot and Structure. Another was Self-Editing for Fiction Writers. The first was very helpful. The second was demoralizing, but also helpful. What a blessing and a curse to see all the cliche, amateur mistakes I'd made! Having written multiple screenplays, even having been paid for one, I didn't consider myself an amateur, but I sure had made some of the mistakes of one. Having an editor read the 2nd draft and give me excellent notes was also invaluable. Needless to say, draft 3 was much stronger.
So, what does this have to do with outlining?
Well, last year I picked up another book: First Draft in 30 Days. Unlike the NanoWriMo method, (which, again, I take no issue with) this book advises outlining, and I find myself being won over. Here's why: My main issue is with plotting. I did some major re-writes during drafts 2 and 3 that I think I could have saved myself with a very detailed outline. In essence, this outline replaces the first draft. It will be 30+ pages by the time I've finished, with every scene mapped out, including objectives, character points of view, etc... Just today I came up with two plot points I'd like to incorporate that I think will strengthen the novel and propel the story to book 3. Had I simply started writing, I'd have to go back and alter all of the scenes which pertained to said plot point changes. (Dialogue, actions, reactions) Now I just need to change a few sentences of an outline.
All this isn't to say that outlining is better than not outlining. I think it depends on what genre you are writing and what you know your writing strengths and weaknesses to be. If you aren't sure yet, just go with whatever feels right for you, and then re-evaluate once you've read the results. I'm very glad I did the freeform NaNoWriMo way. I don't think I'd have finished my novel without that quick first draft. I haven't ruled out doing NanoWriMo again this year, in fact. For book 2 in The Gateway Series, however, I'm trying the detailed outline method. Once I've done it both ways I can make an informed decision on what works best for me.
How about you? Do you like outlining, winging it, or a combination of both?