I tripled the subscriptions for Slidegame.io with a single post on Hacker News that got to number 20 on the main page.
Here's what I learned about how to write a good headline:
Start the Headline with 'Show HN:' if you're linking to your new site or app. This will get you onto the Show page and the main page
Provide a clear benefit for clicking on the link - what will the audience receive in return for their attention
Give your site / app credibility - this may be because of who the author is, how many subscriptions / users you have so far, ratings etc
Give an early reason to sign up / subscribe / buy your product. This will warm the audience up to signing up once they hit your landing page
Include the name of your site - it's already in the link and doesn't make the user want to click
Be generic - instead be very specific about what the person is clicking on and why they should