Why do you want to work with this company? 

Here the interviewer wants to know how well you know about the company and how good you feel about this company as a place to work. Hence you must do some homework before you go to an interview. 

• Research about the company (Website, Social Networks, Wikipedia etc.)
  • What the company is
  • Leadership team (Founder, CEO etc)
  • Vision and Mission of the Company
  • Locations & Mode of Operations
  • Areas of Expertise, Products & Services
• Match up your skills that contributes to the vision and mission of the company

Other tips are:

• Show your trust in the company
• Say it is the best place you can grow and make the best use of your skills
• Say how confident you are about the future of the products/ services of the company with some facts that you learn from research.

Example:

As it is well known, XYZ company is one of the fastest growing companies with such a long long history of leadership in the industry. On top of that, it is the kind of place where I can fit in and excel, so I was thrilled to see you have this opening.  Your company believes in providing superior service, and I share the same value: A place where my skills or background fits perfectly and can be utilized, respectively. I also read what your employees are speaking about and understood that it is a great place to work. It has crossed the branches in the world also and I was in search of this type of company. I believe this is a place I rightly fit in.