What's worked for me:
1. Be genuinely helpful first. Before you promote anything, spend a month just answering questions in communities where your users hang out. Not pitching, just helping. This builds credibility and teaches you what people actually struggle with.
2. Build in public. Share your process, not just the finished product. People love following a journey. Weekly updates on LinkedIn, a Show HN when you hit a milestone, short posts about what you learned.
3. Email still works if you do it right. Collect emails from day one. A simple "get notified when we launch" form captures people who are actually interested. Then nurture them with value, not spam.
4. The 100-user challenge. Instead of trying to reach everyone, focus on getting 100 people to really use and love your product. Those 100 become your advocates and do the marketing for you.
5. Don't spend money on ads until you can articulate exactly who converts and why. Ads amplify what's already working. They don't create product-market fit.
The pessimistic comment about marketing being dead is half-right. Lazy promotion is dead. But genuinely helping people in the right places, over time, still works.
Source: former Head of Growth at a fintech company
Spending money on ads is just burning cash. Posting in online communities will get you immediately banned for spam or unpaid advertising. Social platforms will bury your content without promotion(=burning cash). And sites like HN or Product Hunt will just give you a false hope. Reddit will get you two likes and one page view.
So... don't. The internet has change so much, that it makes no sense any more to try and do anything in this regard.
The only way is to slowly keep pushing it where you can, not intentionally but seize an opportunity if you see one. Don't hope for fast progress. It's a marathon, not a sprint.
Good projects are the type that some people have been building a hack for themselves. Like a system that replaces bookkeeping or records. Payment systems that nobody wants to maintain. Most of the time, it's expensive and inefficient but they just don't have better tools.
Find the people who are doing this. If you can't think of any, well, you might have started wrong and your side project may not be worth anything.
A lot of people are trying to sell fish to the fishermen. It's not that those fish aren't worth anything; it's more that you have to leave the village.
What got me started was sending out letters to clients, in my case schools. Old school I know. I have always worked full time. The sideline has made several hundred thousand dollars over the last 20 years.
Think about how companies advertise and copy with what you can afford.