Like many things, it's usually best to learn on the job, practice, and get better at it after making a ton of mistakes along the way. The problem is, as a start-up, you can't afford to make a ton of mistakes when hiring, and you also can't afford to wait too long to hire when the business is scaling quickly.
The hurdle is, the people that speak problem far out weigh the people that speak solution. You will have your work cut out for you when looking for that one golden egg. However, if you're very careful in your hiring process and ask the right questions hopefully you can avoid making a bad and costly decision.