I hate it when I'm enjoying a story, and at the bottom you get an author’s note which asks for the readers to give the author ideas on what should happen next in the story.
If you want to be the author of your work, then you actually have to come up with your own ideas and write them.
I also find it very risky if you have no idea how your story is going to work; purely because it means that you are more likely to get confused halfway through or lose interest and not finish the story.
Before I start writing any of the chapters, I write a detailed plan as to exactly what happens in each chapter. I update it as I go along, and I do change my mind on the details, but at least I know where I’m heading.
This also allows for me to write certain chunks ahead of time without having to write the in-between bits as well.
The point of most stories, whether fan fiction or otherwise is to have some kind of character development throughout e. g. the protagonist learns a life lesson. As an author you need to know what this is for each character - otherwise what is the point of them even existing within the story?