Comment by throw_me_up

Posting on Reddit or HN is fine, but unlikely to be successful if that is all you do. Cold calling/emailing/linkedin and posting on forums like HN continuously can both help. The latter only works if your solution genuinely solves someone's problem otherwise it will come off spammy. If your solution has obvious keywords and those keywords aren't too expensive, then Google ads can be relatively cheap method to get started too.