P.S. This second point you make is why I prefer to hear about what people DISLIKE in art rather than what they uncritically love. That is where the interesting stuff happens, when you *can't* identify with something, but otherwise endorse it aesthetically...
Actually the first point in any process is deciding what something won't sound like! Once most avenues have been eliminated, a beginning can be made. Then slowly shift the thing into a new position, by a process of rejecting what does not work... very negative I know! I was in a friendly argument with Simon Reynolds last year via email about his proffering up of the Arctic Monkeys as a "good thing" partly because as he said "the raging-against is stronger and more convincing, rhetorically, when there is something to rave-for out there and in 2006 you take your pleasures where you can" but to my mind, providing you have a beginning and a list of dislikes, you have all you need to create something... though this might be an artifact of computer based composition, its more about solving problems...