Writing, for me, is a little like wood carving. You find the lump of tree (the big central theme that gets you started), and you start cutting the shape that you think you want it to be. But you find, if you do it right, that the wood has a grain of its own (characters develop and present new insights, concentrated thinking about the story opens new avenues). If you're sensible, you work with the grain and, if you come across a knot hole, you incorporate that into the design. This is not the same as 'making it up as you go along'; it's a very careful process of control.
Terry Pratchett5.Buggre Alle this for a Larke I amme sick to mye Hart of typefetinge. Master Biltonn if no Gentelmann, and Master Scagges now more that a tighte fisted Southwarke Knobbefticke. I telle you, onne a daye laike thif Ennywone withe half and oz of Sense shoulde bee oute in the Suneshain, ane nott Stucke here alle the lielong dale inn thif mowldey olde By-Our-Lady Workefhoppe *AE@;I*
Terry PratchettThis man was so absent-mindedly clever that he could paint pictures that didnโt just follow you around the room but went home with you and did the washing-up.
Terry Pratchett