I've never been much for plotting out my stories. I like to sit down and see where the characters take me. Sometimes it works...other times not so much.
I'm not against plotting, it just doesn't work for me. I've tried to sit down and determine how the story should go, but I find that if I force myself, the ideas refuse to come. I get my best ideas when I'm "in character" writing.
When I started writing the urban fantasy manuscript that I'm now querying, I knew who I wanted the main character to be. I thought he'd be divorced, with a bit of a drinking problem, in his mid-30s, and not want to be tied down. Well, when I started writing Cole (actually, he started out as Logan), he basically laughed at me. He kept the jaded sarcasm I had planned, but everything else went out the window. He ended up being in his late-20s, never been married, and wanting a commitment from his sort-of girlfriend. When I met a paramedic in the opening scene, I thought she would be his love interest. Well, he had other plans again. Ali, who I'd intended to be a passing character ended up being his love interest and is now getting her own book. I'm quite happy with the way things turned out and the unplanned characters who appeared. There were a few times a character popped up and I said, "Why hello! Who are you?"
That's some of the fun of being a pantser, exploring the story and following the characters. Some people who plot do this as well, even if it messes up their plans.
This doesn't just happen with the characters, it also happens with the plot. I often start with a concept and a plot. Sometimes I know the subplots, most of the time I don't. Sometimes I know the ending, but not always. It's not always easy to write when you're not 100% sure where you're going. It takes a lot of trust in your characters. I do spend a lot of time reminding myself to just go with it and anything I don't like can be changed or dropped during revisions. I also tend to leave some blanks that need to be filled in when I've got a good handle on the story.
Once I get that first story written, and have explored the world and characters, I often know where the rest of the series will go and have more specific things planned for the books to follow. For the book I'm querying now, I have three or four more planned. Maybe not enough for full plots, but enough that I have lots of notes on things I want to happen.
Being a pantser can mean more editing time. So the time spent pre-planning is often spent refining the story on the second or third draft. Once I finish my first draft, I've started taking cue cards and writing all the major points on them. Then I lay them out and shuffle them around looking for scenes to move, delete, add in, or blend together.
I also find that pantsing can lead to exploratory writing. I often write scenes that are more for my discovery of the story or character that don't make it into the final version. I keep a folder of deleted or original scenes because I'm always worried I'll need them. That doesn't happen too often though.
Everyone's writing process is different. You have to do what works for you. But no matter what your process is, be ready to change it if you find something else that works.
What do you find works best for you?