Ideas are solutions to problems. An idea is the start of a deep exploration of the problems people have. This mindset is how you discover great ideas worth pursuing. The problem should be a top priority for your target audience. Choose a problem that enough people need solved so you can ensure that your business actually gets users/customers. I like to assess the frequency, urgency and pain of a problem.
The key to finding a good idea is to get excited about the problem. Love the problem(s) you are solving, not your initial idea or current solution in have in mind.