An interview almost invariably closes with the potential employer asking if you have any questions. Often an applicant will ask for clarification on benefits -insurance, vacation time, etc. While these are obviously important for you to know, they plant a seed in the interviewer’s mind that maybe you are more interested in what the job can do for you than in how you can help the employer.
Try to have three or four questions ready to ask that demonstrate your interest in the company and your desire to be a problem-solver.
If you have been able to do some research, trot out a question or two that came to mind. If you have been able to come up with some ideas that relate to the problem, throw them out to see how the employer reacts.
If you have been able to identify some trends or problems in the industry, ask how that is going to affect the company and what they are doing to deal with it. Show your concern about industry developments and what that may bode for the future.
If some current challenges have been brought up earlier in the interview, ask for clarification and more detail.
The more the interviewer interacts with you as if your concerns are mutual, and that possible solutions are something you could consider together, the more you will be seen as a valuable future member of his team and the more likely you will be asked to join that team.