My number one marketing approach by far has been to tailor the site to the HN audience.
I do this primarily by asking questions that people on HN always like to see answered (how much money are you making? how did you come up with the idea? what tech did you use? what are your best marketing channels? etc). Lots of similar sites don't ask any of these questions, especially not the revenue one.
I tend to share the most interesting interviews with the HN audience every couple weeks or so, and they usually do pretty well!