As dumb as this might sound, I think timing is important.

I am going to make a broad generalization that most of our readers are located between Eastern and Pacific time. I would expect most activity to happen during common down times in the work day (eg. after lunch, post scrum). I think this is essential for generating meaningful and well thought responses.

Perhaps you can do some time analysis on some of the most successful Ask HN threads and tell us your findings :)

Also popular threads like "Who's hiring/firing etc" always happen at the beginning of the month, am now programmed to expect those.

Best of luck