Over the years I've tried to plot my stories beforehand, but it's never felt comfortable. Then I started creating outlines and that seemed easier for me.
A lot of the time I have an idea but it's always subject to change. That makes it challenging for me to write faster. So I've learned to accept that the book is going to take the time that it takes.
Usually, my story begins as a conversation in my mind between the characters. I might not know who the characters are at first, that takes more writing. Eventually I get an idea of who these characters are and what is happening in their world.
Since my stories are character-driven (as opposed to plot-driven) I have to get a feeling of who the characters are. What do they want? What are they hoping to achieve? It might take a lot of writing before I have those answers.
Finally, once I've written several scenes, I have an idea of what the story is about. At that point I may write an outline so that I'll have a rough idea of how the story will go. I'm a "pantser" and not a plotter, so my story may change a lot as I work on it. I don't always stick to the outline, instead I use it for guidance.
For my latest book, Blood Red Moon, I had a rough idea of the first chapter of the story, but I made a lot of changes to it. My original idea was to have Avani and Derek as adversaries without a prior relationship. However, in the final version I wanted them to be long lost lovers. As I wrote the different drafts, I had more of an idea of the vampire and shifter cultures. It took a lot of writing and working on the story before the backstory made sense to me.
As I wrote and edited, I had more of an idea of how the story would go and how it would end. In fact, I wrote the ending before I finished writing the last third of the book. I knew where I wanted the story to go, and with each version of the draft I understood how to get the characters there.
Often the completed story ends up being more than I expected. I may not know what the story will be when I first start out, but it's rewarding to go from the initial idea to a fully developed story.