what is the best time/way to do a show HN?
I've had good luck with a few posts around 7:30-8am Eastern US time (12pm UTC) on weekdays. Otherwise there's nothing really special you need to do. If you've hung around that community for a while I think you can get a good feel for what people like. Of course the more relevant the post is, the better it'll do.
I usually do it around 7-8 am SF time when the new page is still moving slow. Then post it around. I've gotten to the frontpage twice with that strategy, once to no.2