When I started writing my current story I had no plot. In fact I had nothing. I just sat down one day and started writing in an effort to see what turned out. Now that I am returning to the story properly, I looked through the various plotlines trying to work out how to mesh them together. In the end some were set aside for use another day leaving just two main plotlines. It took some thinking and pondering of ideas to figure out a way to mesh them properly so they connected and told a single over-all story. It has breathed some fresh life into the story, now that I know where it is going and how it will end.
A trend of late in fantasy stories seem to be to churn out large volumes containing literally dozens of plotlines that seemingly have no connection to each other beyond being in the same setting. In the long run, ten books in, they may connect, but in the current book they may never meet.
If you look at Lord of the Rings, it had three main plotlines. The first was of course Frodo and Sam. Aragorn, Gimli and Legolas made the second and Merry and Pippin the third. There were other, lesser plotlines – such as Gandalf, Eowyn, Boromir and the like – but they wove in and out as needed. Those three main plotlines kept touching on each other even when they weren’t connected and in the end of the story they formed the whole story.
If you look at the late Robert Jordan and the current Stephen Erikson on the other hand, they stuff their novels with so many plotlines and characters that it is a struggle to keep track of them all – especially when a book can go by in which the plots followed never once met up or even mention each other. They are like two or three different books cut apart and then pasted together.
I think initially that was a way my current work was going – but I have since changed it. Yes, there are other stories of other people I wish to tell in that setting, but I won’t mash them all up together. Instead they will follow separately, hopefully, in their own work so that their stories aren’t lost amongst all the others.