Check out a list of questions you could to ask the interviewer about the company and co-workers:
Which competitor worries you the most?
You should ask this question if the recruiter doesn't mention competitors. Asking about competitors is a must because this is one of the biggest concerns of any business. Asking about competitors will demonstrate your approach to problems the company is facing.
How do you see this position evolving in the next three years?
Ask this question to show interest in further career opportunities within the company.
Can you tell me about the team?
This question tells you about the individuals you will interact with on a daily basis.
What is your vision for where the company or department will be in 3-5 years?
This is a good question for the direct supervisor. He will give you his personal vision of the company. The question reminds the supervisor to think and remember where the company is headed.
If you could improve one thing about the company, what would it be?
The employer will give you an idea of what his priorities are or the challenges/problems that worry him.
What's a key to this company's success that somebody from outside the company wouldn't know about?
The recruiter should be proud about essential components of the company. It might be the CEO, the three-year plan, financial results or a strong team. Ask this question and you will have a positive answer.