Zero words written, zero words to edit. Blank pages, finished pages. Zero is both the beginning point and the end point for me.
Nothing is more exciting (and slightly intimidating) than that blank page. Even more intimidating, a new notebook, perfect, like freshly fallen snow...if snow had faint parallel lines in it, anyway. I buy linen backed A5 notebooks from Paperchase - the paper is think enough not to bleed through and they stand well on the bookshelf. They are also packed with pages, so I don't have to replace them...going through that horrible moment of taking a new one off the shelf and spoiling it. The computer screen is neither so personal nor so permanent, and having a new story fermenting in my head makes me let it loose on the cyber page. I love starting things. I can write the first 10k of a novel over a frantic weekend.
Editing and rewriting is harder. At the moment I have, according to my agent, an excellent first 20 chapters and a lovely last 20 chapters. But the book has a sagging, lumpy middle (my words, not hers) that need a change. I've worked out where the problem is and am fixing it, but have to rewrite a number of bits. You move one thing, and everything moves. I've decided to bring the character in earlier and make him more prominent, so I'm having to check every scene he's in subsequently, or any scene where they meet him to make sure it still works. I printed off the hundred pages concerned, and am working through them, first with a red pen and next on the computer. When I get to zero pages, it's one more read through of the whole lot, and it's back to the agent. Beginnings and endings, the easy bits. The trick is to get better at the middles.