What are the lesser-known do's and dont's for a product launch on HN?

Mostly curb your enthusiasm. For most products your customer is not here or is vastly outnumbered by gawkers. (e.g. also don’t take Product Hunt too seriously unless you are looking for a prize for the best hustle cosplay)

Try turning on the “showdead” option on your profile and you will notice a shocking rate of submissions get hellbanned immediately because they are submitted by somebody who keeps posting articles from their same site over and over again but never any other site. Don’t be that guy. If you are participating like a real person you sure can self-promote some of the time but don’t let that be all you do.

(Pro tip: it’s a good thing you asked because the above policy is applied so vigorously that you shouldn’t really post your own link until you’ve posted a few other links and had one get, say, 25 or more votes)

Post something really interesting and/or get lucky you will get a few 10,000 views but you are still going to wake up the next day and have the job of busting your tail to talk to customers, talk to customers and then talk some more.

Recognize how much luck it takes to “get lucky” and please don’t kill your startup by asking for people to join a waitlist. If you do get somebody’s attention get them to strike when the iron is hot.

Just show it. HN folks are curious types. Give them the keys, they'll take it for a drive, be pedantic about flaws they don't really care about, and then buy it. You shouldn't have to explain it very much.

That's also why waitlists are frowned upon here. There's little to play with and no buy button. The final product can also be quite different.

There's usually a lot of negative comments on Show HN. That's because there's no downvote for topics here. People who like it upvote without comment, those who don't usually leave a comment. And frequently they get to the point, without thanking and such. Don't be discouraged by those.