"Questions for us" - remember that interviews are two-way. You're also finding out if you want to work for them. So think about the things which are important to you and what you want from a job, and base questions around that. You could ask questions about:
- flexible working (can you work from home?)
- is there much travel to other sites or overseas?
- how many people are there in the team?
- why is there a vacancy (they'll probably not tell you the complete truth if it happens to be, "Because we've got a nightmare manager and a really high turnover as a result.")
- what opportunities are there for training?
- what benefits are there? (Private health, pension, gym, that sort of thing.)
There could be questions which are particularly related to the role in question, or the industry. In my case, because of my line of work, I tend to ask things like,
- Is there any datacentre work?
- What's a typical on-call week like?
- Are there any women in the department?
But they're not questions which will be relevant to every job. Maybe a school job, you could ask questions about policies on uniform, punishment, homework, whatever.
Try to avoid things which are easily found on their website, unless it's in terms of, "I saw on the website that you offer X - can you tell me more about that, please?" Obviously, you can only avoid that sort of thing if you know what is on their website, and if you're going for an interview, you should have done that research.
It's also okay not to have questions, particularly if you can phrase it along the lines, "I did have some queries about the grading structure, but you already covered that when you were talking about typical career paths," because that shows you had had some questions prepared.
Just think about what would make it a good job for you, and as the interview progresses, consider whether you're getting an idea of whether those values/needs in you are likely to be met, and if it's not clear, then ask questions which will help clarify it. If you've got a pen and notebook with you, you can always make a note to yourself if something comes up you want to find more detail about.
Obviously if it's a case of, "I don't care, I just need to have an income again," try not to let desperation show!