It would be interesting to explore how to encourage replies and retweets. This applies to all social media, really. The more people talk to you, and you reply to them, the more invested they are and the more likely they are to share your content.
Asking questions is a good start. But you can also use polls, run competitions, set challenges. It also helps to post personal content and use humor too. That makes the channel feel more personal and encourages interaction.
Posting entertaining, helpful, or inspirational content is a big factor too. Too many Twitter channels seem to be an endless stream of news nobody cares about.
I also think we can be somewhat delusional about what people will find interesting. Our content needs to be about our audience and not us if we want their attention.