How do you come up with ideas for new features (products)?

I think the best way to do this is to see what the demand is by looking at already existing customers. For example, if your customers find one process of using your software too tedious, maybe you can design a new feature that gives them a shortcut. You can get customer feedback by surveys or asking for customer interviews for more detailed feedback. However, I think it's easy to fall into the trap of "more features", but I think what most people should keep in mind is that oftentimes improving existing features or the features that customers use the most (80/20 rule) is more important than putting in mediocre new features.