In order to present yourself well at a job interview, you need to prepare in detail. You have to thoroughly research the company and the principle goals of the organization. Once you've done that, you will want target your responses to the skills and attributes they are seeking in a future employee.
One of the only times I have felt like a spy was when I was job searching while currently employed. You feel like you're a double agent. You're always searching for new leads, you need to pledge loyalty to both sides before jumping ship, and you need to conduct your operation under the radar. If you get caught, it's all over.