Many try by just talking to a developer. At that point you’re effectively just listening to a sales pitch. That’s an important skill for developers to have to get jobs, but that’s not the skill you would hire a developer for. You hire them to write software. Being able to pitch themselves does not correlate to being able to build software well.
This is also a fantastic opportunity for you to test out working on real problems with the developer. Many of your interactions with a development team would be about product use cases and the necessary data involved. If you find that you and a developer are communicating well on this issue and you think they have a firm grasp of the data needed in your product, then they are likely to have a solid foundation for the software that needs to be built. This isn’t a perfect correlation with great coding ability, but great coding ability won’t matter if the software is built on a poor foundation.
These steps won’t ensure a 100% success rate when hiring developers. Like I said, it is a hard problem even for seasoned developers. While these steps will increase likelihood of success, there is still lots of risk. Good hiring is never a guarantee. But then again, neither is starting a successful business.