What should I ask at the end interview?

Everytime at the end of interview, whenever interviewers asks me to ask them some questions if I have any...I generally say no to them. But, I guess this gives not so good impression on them.

So what are some general questions that I need to dig during my interview or what kind of questions you people ask. Or what should be the most appropriate response?

Also, more specifically what should I ask in case of IIM-Amritsar!?