Simple way is to check what products your competitors are selling, buy them find a weakness or many and create a new product to fulfill without those weaknesses!
Always put yourself in your prospects "shoes" to know what will benefit them. All products have weaknesses including your competitors, if you know your prospects enough you'll figure out those weaknesses better!
Improve upon the existing product then too, make it better - if it's an ebook add more to it and make it a course...