I do a sort of semi-planning, I suppose. Usually, this is how I start. 1) Lay on my bed, laptop flung to the side somewhere. 2) Think of what kind genre I feel like writing in 3) Devise up a character and plot out their backstory in my mind 4) Think about the larger picture some more 5) Log on to computer and IM while thinking about new book 6) Keep awake until 2am 7) Open Penzu, LJ, FFnet or Word and plot out the beginning 8) In my tired, delusional state, I keep writing and writing whatever comes to mind. The outline gets longer and longer, inspiration hits me again and again. 9) I look at the clock and it's 7am. I look at my screen, and I've non-stop typed thousands of words 10) Without going over it, I go to sleep. 11) In the afternoon, I open it back up and compliment my self on how brilliant I am. Works every time ;P Though while I'm writing, things will change, but it still sort-of follows the skeleton I created. Over time I add onto that outline, making the world deeper and constructing more characters.
I don't really plan. I get an idea for a plot, I know roughly where it starts and ends and the important parts inbetween. I know my characters and how they relate to eachother. Location isn't an issue for me, I usually pick locations I am familiar with so that isn't difficult. The problem with too much planning for me is first off, I get bored with planning because I want to "begin", especially since I am *always* planning in my head. Pretty much whenever I am idle I am thinking about it. Secondly, I keep changing things, so I'd have to keep changing my written plans and then I'd never begin anything. I think for me it's best to have a rough idea but not a strict plan as that way I am free to go with any changes I make and I can always edit my work as much as I want. If my work seems unorganised and scatty I can change that afterwards and polish things up.
I don't really plan. I get an idea for a plot, I know roughly where it starts and ends and the important parts inbetween. I know my characters and how they relate to eachother. Location isn't an issue for me, I usually pick locations I am familiar with so that isn't difficult. The problem with too much planning for me is first off, I get bored with planning because I want to "begin", especially since I am *always* planning in my head. Pretty much whenever I am idle I am thinking about it. Secondly, I keep changing things, so I'd have to keep changing my written plans and then I'd never begin anything. I think for me it's best to have a rough idea but not a strict plan as that way I am free to go with any changes I make and I can always edit my work as much as I want. If my work seems unorganised and scatty I can change that afterwards and polish things up.
Like so many have said; it's different for everyone. I think planning is essential but there is merit in restricting how much you plan. You can plan a story all you want but until you start writing it may all be meaningless. The good thing about a plan is that it allows you to put things into perspective; see how ideas, plots, characters and the like relate to each other and if it all works. But you shouldn't get caught up in the whole planning process and forget to write.
When an idea hits you, but you don't know all the details about it just yet, write the idea down. Maybe even just start writing. Don't let the fact that you haven't worked out all the kinks in your story yet stop you. Just write.