A while back, I wrote a little app that tracks the relative scores of new submissions and the front page, which tries to tell you when would be a good time to post: http://hnnotify.leknarf.net/

The twitter notification part broke at some point (I haven't had time to fix it), but the main chart is surprisingly accurate. It shows that it's been a good time to post for the last hour or so, so this submission was very well timed. That other submission was sent at a particularly poor time (about 2 hours ago), when few people were upvoting on the new page.

Timing really does make a big difference.