You can ask what the customers want. [Uh oh. Get ready to hear about Henry Ford and the horse.]
You can look at what they've always wanted and then, after some modifications, put together a slick (New and Improved!) campaign to sell it to them.
Or you can get to know the customers so well that you have a sense of what they want before they do. [Cue Steve Jobs.]
That last one can be far more risky but it also may be the most rewarding.
Just don't believe in magic more than in the basics.