Speech is free, listening is priceless.

But seriously I have tried to market quite a few things and the normal condition is that people are indifferent and you have to work about 25x harder than you think [1] to get people's attention. Maybe 1 time in 10 or less you have something that resonates with people and that they get excited about.

[1] not hyperbole!

Well, it depends on what your product is. (I presume your story is about the product being useful.)

If it's your product, and it's a tech product, it might be appropriate for "Show HN". If you do, though, the tone should be "hey, you might find this interesting", rather than a sales job.

If the product solves a problem, you might find a Reddit sub about the problem.

Beyond that... I don't know.