Post contrarian opinions but succinctly and with room for people to correct / refine your points ("strong opinions, weakly held"). My experience is that wishy-washy comments don't go far here but opinionated ones do, even if they're wrong.

Don't be afraid to post the first comment on a submission on the new page with the hope of kickstarting the discussion.

That said, I don't know that HN karma matters for much in the real world.

As far as time zones, anecdotally HN seems to be most active during the workday on west coast time.