It's just a mindset.

People complain about things all the time. As you listen/watch/read/etc, listen to their complaints, and think about how you might make that situation better with technology you're familiar with. I find that I think of several ideas a week with this approach.

The next step is to think about the product definition. What _exactly_ does it do? How does it work? How much will that cost to operate? How much is it worth to the potential customer? Given those two figures, is this going to be an opportunity you want to investigate further?

If it passes the first simple tests, then you need to expand a bit: how many possible customers are there? Is it tied to geography or language or culture? How will you market the product, and what will acquiring a customer cost you? Do you have a free tier? A trial period? Can there be a premium tier?

If you can get past this basic analysis, then you need to put some more time into it. Most ideas won't get this far. You should now try to actually talk to some potential customers, see if your idea will actually work for them, and refine the product itself, its business model, and the implementation costs.

There are many, many websites that describe how to do this. If you're not already a reader, maybe try indiehackers.com as a starting point?

There are problems everywhere. Start with problems that you have that you would realistically pay to solve. Solve them in a way that can be sold as a service to others. Then sell it as a service.