There are few questions that I get asked more frequently than the perennial "How much should you plan and outline before you start writing?" Sadly the answer, as it is to many other questions, is "it depends". If you have spent anytime around the world of literature, writing, and publishing then you know that rules are meant to be broken. There are very few rules that are cut in stone and the question of "planning" falls into this category. I can't possibly tell you the answer to this and how you should approach your own writing. However, what I can do is tell you what I do and how it works for me.
The first thing that I think about is the message that I want to convey in my writing. What platform best suits conveying that message? A short story? A novel? An essay? What about a play or screenplay? That is the first step. If your message is the decline of capitalism then maybe a novel is the best idea. Conversely, if the message is just an appreciation of baseball then maybe a short story or essay is best.
When writing short stories I normally do not do any planning or outlining. I generate my idea, wherever it may come from, and write. I see where my mind takes me. I explore all or the possible permutations and versions of the idea that my mind allows. I generally push the envelope and often times fail. After I finish the first draft I reread it and see if there is anything salvageable. Sometimes, like now, a short story inspires me to stretch the idea into a novel. Other times the story is not very good and I file it away to read again at a later date.
-Never delete anything. You never know what a later reading of something you previously wrote will inspire. I often times find myself rereading stories that I had previously discarded only to find some redeeming value in them.
When writing a novel I find that my process is a little different than most main-stream authors I read. I start with my idea and think of a situation and characters who can best help me flesh out and explore that idea. That is the extent of my planning for the first draft. I have my central theme, my characters, and my conflict. The rest is pure creation while I am writing and that's just the way that I like it. I tinkered with outlining and much more in depth planning and found the writing to be less fun. It felt scripted, tired, forced, and boring. I find that the lack of planning for my first draft allows my writing to be more exploratory and inspired.
After my first draft is complete I leave it alone for a month or two and forget about it. I try to forget the words that I wrote and as much of the plot as I possibly can. This allows me to view it with fresh eyes and have a much more independent and truthful reading of it. I look for major plot holes and just general mistakes. After that is finished I start my first rewrite. This rewrite, the most important of the drafts, is highly planned. I have already had the freedom to explore my ideas in the first draft and in the second draft I have the opportunity to keep what worked and discard the garbage.
The second draft is outlined to the point that at the end of each day I know what I am going to write the next day. I include notes of good scenes and lines from the first draft that I need to make sure to include as well as notes of things to make sure I avoid. And, not surprisingly, I find this second draft to be the most important, inventive, and fun to write. Since I already have the majority of my plot mapped out and my characters fully formed I have the freedom to experiment with dialogue, structure, style, tone, and imagery. All of my energy can be completely focused on the art of writing and the style in which I portray my message.
Of course, everything listed above is my personal preference and is only "right" in the sense that it is right for me. It works for me and enables me to produce my best work. The key to becoming a good writer, other than practice, is to develop a method and habits that help you to produce the best writing that you are capable of.