This is a toughie, but one you can be sure you'll be asked. Definitely keep things positive—you have nothing to gain by being negative about your past employers. Instead, frame things in a way that shows that you're eager to take on new opportunities and that the role you’re interviewing for is a better fit for you than your current or last position. For example, “I’d really love to be part of product development from beginning to end, and I know I’d have that opportunity here.” And if you were let go? Keep it simple: “Unfortunately, I was let go,” is a totally OK answer.
Any candidate can read and regurgitate the company’s “About” page. So, when interviewers ask this, they aren't necessarily trying to gauge whether you understand the mission—they want to know whether you care about it. Start with one line that shows you understand the company's goals, using a couple key words and phrases from the website, but then go on to make it personal. Say, “I’m personally drawn to this mission because…” or “I really believe in this approach because…” and share a personal example or two.
Whenever possible, you should speak about your achievements from the perspective of an employer (helping them to find new customers, helping them to improve their reputation, building good atmosphere on the workplace, earning more money, etc), rather than achievements from your own perspective (getting promoted, earning a degree or certification, etc).
Example: “What I liked most about my last position the ability contribute in a collaborative way with other teams. Each team member was encouraged to bring new ideas to the project which were respectfully considered by all. For example, we once worked with a client who was relying on us to solve a critical issue. Our team met to discuss the situation. After I recommended a plan to resolve the issue, we took time considering the pros and the cons of the solution, building on how to make the idea better and more comprehensive. When we implemented it, it worked better and faster than everyone expected. The client was very pleased.”
Start by explaining what you'd need to do to get ramped up. What information would you need? What parts of the company would you need to familiarize yourself with? What other employees would you want to sit down with? Next, choose a couple of areas where you think you can make meaningful contributions right away. (e.g., “I think a great starter project would be diving into your email marketing campaigns and setting up a tracking system for them.”) Sure, if you get the job, you (or your new employer) might decide there’s a better starting place, but having an answer prepared will show the interviewer where you can add immediate impact—and that you’re excited to get started.
What Interview Questions to Ask Candidates?