Give direct, honest answers. Take your time. Develop the answer in your head before you respond. If you don't understand a question, ask for it to be repeated or clarified. You don't have to rush, but don't be indecisive.
Ask questions in return.
Be prepared. Answering difficult questions that may reflect negatively on you can be answered by using the "sandwich model." This model has a positive statement followed by admitting the negative situation, and ending with another positive statement about what you've done to overcome the problem. Ending with a positive statement leaves a positive impression. Anticipate tough questions and practice interviewing beforehand.
Try a few of these examples as a tactic to answering this hardest of questions.
Or, if you were fired, career expert and columnist Joyce Lain Kennedy suggests several great answers, among them the following.
I've been busy going to school full time (specify), raising two children and managing my home. Doing that on a daily basis gave me a lot of skills we generally don't acknowledge, like leadership, time management, teaching, coordination, planning and so forth.
I needed to address some health issues. It would not have been fair to an employer if I took too much time off from work. I'm now ready to return to work and give you 100 percent.
I was trained in machine operation while at a correctional facility. I have now completed my GED and am ready to work for you.