I keep saying that I am a "pantser" - that I write by the seat of my pants. And that is very true. But it is also true that I like to have at least a bare bones outline, so that I have a clue where my story is going, and how my characters relate to each other. Without that, they could get into all kinds of trouble! Knowing where I am going (and yes, this can change as I write) creates boundaries for me to work within. They don't stifle me, but they do give me a grid to work within.
If I try and stay within the confines of this grid (which can get very complex!), I have to do less rewriting. It is not at all fun when you realize that your chapters don't hold together ... and that they aren't holding together in a very glaring fashion! Definitely a "How could I have done that!" moment. Hopefully, I have learned from my experiences.
I work with a bare bones outline - but it is an outline. It not only keeps me organized (very important for us Cappies!), but it allows me to revise in a timely manner, without having to look things up, or sit there wondering how I got to where I am in my story. I actually love to do the outlines for my stories - it is a wonderful way for me to get into the creative process. I put down whatever comes to mind, then go back and edit it to bring the elements together, and take out elements that obviously are not going to work. Saves me time, saves me headaches, and my fur kids have a happier mommie!
What can your outline do for you? For a mystery writer like me, it can help establish clear motives. (Readers tend to wander off without finishing a book when things like motives are not clear.) The primary plot and the sub-plots are able to sort themselves out. (The sub plots make the story, IMHO. I just finished reading "Stranger In The Room", by Amanda Kyle Williams, and the sub plots are so finely woven in that the story just flows - one never questions what is going on, or why.)And ... your story stays on track ... no wandering off into its own little world!
One last word on outlines - you can do them however you please! Write them in a file, in traditional outline format. Get out the junior high index cards and work with them. Go high-tech with a spreadsheet (very cool, but not for a non-techie like me!), or use writing software of some type (there are plenty of options out there!).
It doesn't matter how you plan your story ... it just matters THAT you plan it!