Look for problems. It's hard to sit and think of ideas, even if you do, most of the ideas will change on contact with potential customers.

Look at what you're strong at and what you enjoy. If you're seeing customers struggle with other businesses solutions, then there might be a way to solve that problem in a better way.

Being a good listener helps - get the feedback loop going as quickly as possible. Don't take anything personally if a customer doesn't like what you're doing. They could be right. Iterate on the initial idea. Don't spend too long building the first version of anything as it'll probably look different in a year.