Don't.

Yes, discoverability is broken. But that doesn't justify spamming, or other "growth hacking" that the Product Hunt culture has made socially acceptable (in fact, there has been a rise in clever voting manipulation tactics on Hacker News because such tactics have been normalized on PH: https://twitter.com/jiyinyiyong/status/855661997169364993).

Spamming won't magically make you go viral. And if you don't go viral, that's ok. Improve and try again.

of course once they did it they where quick to plug the hole and denounce it as unhetical

spamming of course isn't a cost effective solution to reach people needing a product, but social network propagation trough referral still is highly effective

you can also buy targeted mailing addresses from selected companies, but the big, accurate lists are costly to come by - but those give you an incredibly focused group

Now, maybe, I don't know what you mean by "product startup", or even the word "most", but having burned a fair amount of shoe leather in my time, and having been associated with startups that have done nigh on a billion (USD) in sales by talking to customers, in their shops, and showing them goods, and signing contracts for delivery and SLAs, I surely would like you to back up this assertion.

Promoting your product via Twitter or your friends is fine. (promoting a submission on Hacker News [i.e. highlighting the submission itself in an attempt to vote manipulate] is against the site rules, which is not spam but still bad)

As an example:

https://news.ycombinator.com/item?id=14202456

b) I don't have to promote to all 125 sites, I can be more targeted.

c) You're automatically treating growth hacking as spam. Growth Hacking is a common promotion process - the issue is how it is accomplished. Promoting on lists - good. Making fake websites with fake articles / reviews - not so good. Paying bots to upvote - bad.

(I'm not suggesting this is a good idea!)

For example, say you're building an Android weather widget (for some reason). Build a profile where you're an 'Android', 'Widget', 'Weather' expert and Quora will surface this question for you to answer* : https://www.quora.com/Android-Application-Which-is-the-best-...

This targeted approach is much more valuable for your product, your time, and for the person asking the question.

*Of course it helps to actually have the best weather widget.

Sure, if the problem is unsolved then it is appropriate. But more often than not, this kind of advertising drowns out actually useful answers. Not least because their 'walk the dinosaur' narrative construction disguises that they are ads until you've read the whole thing.

Never heard this term before, what does it mean?

http://knowyourmeme.com/memes/everybody-walk-the-dinosaur

At the nascent stages, you don't need to add numbers, only people who are delighted to use your product and are willing to pay for it.

I found this fascinating. shows the hard work needed to capture a real audience, as opposed to paid eyeballs.