My first lesson (again, this lesson comes back to haunt me) is to NEVER throw anything out. Words, I mean. I don't care about other stuff. Other stuff can be replaced. Words not so much.
See, what the average author does is write and write and write and so much of it is rubbish that the writer despairs of ever being anything more than a hack. It's disgusting garbage the writer churns up in an effort to get at what the story is all about. The essential truth of the thing. The purpose, the meaning, the freaking point.
And then, eventually, it becomes clear. This is the point I reached at the beginning of September with THE RIVER BRIDE. Now that it's clear though, I realize a lot of my earlier churn contained shards of gold. In whole pages of dreck are one or two useful observations. A couple of truths. I remember writing them. Can I find them again? NO! Because I cut and deleted and said, "Oh, lord, you'll never want THAT again."
Churn. Never underestimate its power.