What suggestions do you have for improving my paper?
The question "What do you like best about my introduction?" would be a helpful open-ended question to ask after someone has read your paper.
A helpful open-ended question for asking feedback on a paper would be: "What are your thoughts on my paper?" This question allows the reader to provide their opinion and feedback in a more comprehensive manner, giving you a wider range of insights about your writing. Additionally, you can ask specific follow-up questions like "What aspects stood out to you?" or "Are there any areas that could be improved?" to get more targeted feedback.