The redoubtable Roger Morris (and his evil twin RN Morris), author of Taking Comfort and A Gentle Axe, left a description of his working method in the Comments trail. I have to say that some of Roger's tactics must be unique. In particular, Roger is the only writer I've heard of who includes tracing paper in his working methodology. (I hoping he'll show me how he does this, since I find it hard to picture. [Roger has elaborated in the Comment trail below.] When he donates his papers to his alma mater, he needs to include the tracing paper; this will greatly baffle future scholars, and possibly form the basis of some 22nd-century Da Vinci Code-type novel):
I'm trying to think of my writing method. I used to dive in with only the vaguest idea of where I was going. But several unpublished novels later, I worked out that I needed to do a little bit more planning. I like to do what I call 'cooking' where I just mull over things for a long time. If I'm writing one of my crime novels everything has to be really plotted out. I now use sheets of A3 tracing paper to write my story strands on. I can lay them over each other to see how the layers connect. I also have to work out a time line pretty tightly. But even Taking Comfort, which was not so much a genre crime novel, had a lot of work put into the story. I treated it a little like a screenplay - you know, structure is story (now who said that?). In fact, I wrote it as a screenplay at one point. Then I realised it had to be a novel.
Another thing I do when I'm starting out is get a lot of different coloured index cards and different coloured pens. I write character details on the cards - colour coded depended on which plotline they fit in with mainly. Of course, the characters overlap, but they usually belong to one strand or another. Then I completely ignore the cards and write the book. (Well, sometimes I check back, just to make sure I keep things consistent.)
In my crime books (2 written so far, so that hardly qualifies me to speak with any great authority - but I do what I do) I also find it quite useful to write a developed chapter by chapter synopsis, before writing the book itself. In this synopsis, the final denouement will be written quite fully, with a fair amount of the dialogue in place. I have found both times that I have used a lot of this dialogue when I actually get to the writing itself. So I suppose what I do is write the ending first! Weird, hey?