I was talking to Scowie the other week about composition (songs for me poems for him), and we agreed that if you don't feel that it's starting to hang together within about 15 to 20 minutes it's probably not worth bothering with. Better to work on another subject then come back and start again from scratch.

For me the start is usually a single phrase with tune attached that just comes into my head. Mostly the rest is in place within 10 minutes and then I try to forget it and leave it for a day so that I can come back and read it more objectively to edit it. This involves looking for more exact wording where meanings are unclear and trying it out to see if I unconciously change things by using my natural speech patterns. What you naturally say is not neccessarily the same phrase that you would write.