I've seen a lot of advice that says you should plan your novel before you start to write it. But then I've heard hugely successful novelists say they start with a small idea and then just start writing and the novel develops as they go along. I follow the latter. I very much just start writing and the story changes and develops as I write. I don't think there is any right or wrong way, but just wondering what everyone else does?
I usually have a plot to start with. But the flow automatically sets in place once I start penning down the words. I do get stuck at times, and then, I plan the next 10,000 words, or the next 5 pages. And then stick to this format. I aim to complete the story first, and then go for refining, refining, refining.
I recently saw an ITW of Jeffrey Eugenides, telling how what was only menat to be a subplot with secondary charchters, developped into a whole story, and how he quiet quickly abandonned the story he was writing to concentrate on this subplot, who became a whole novel (his last one I think)
So, I think it's good to plan a novel, to have some structure, some landmarks to help you not loose your course, but, no matter how much you've planned your novel, at the end, It is always going to be something different from what you tought !
Like you i'm just starting my first draft. It too all began with a simple idea which has grown with time. I think having a skeletal structure to build on in terms of the plot was really helpful to me though. Even if it's just a short concise description of each chapter. I have deviated from this many times and my story now looks nothing like I imagine it would. However what this method gave me most is some much need direction, a starting point.
I really don't think there is any right or wrong way to do it. Too much prep work can be an inhibitor in a lot of ways. Too little prep and you could be left scratching your head for long periods wondering where to take the story next. When writing a fictional piece the freer your imagination the better in my humble opinion. It all boils down to what ever works best for you.