However, please don’t feel limited to these topics alone! If there’s something you need to know, and can find the answers by asking your users, make sure to include a few questions about it (as long as it’s not offensive or threatening of course!).
There is also a special type of user interview known as the contextual interview. This is an interview which is conducted after (or during) a user observation—it’s an interview “in context” with usage. You’ll find these are very common in usability testing, the assessment of products and even in information visualization.