The #1 rule of answering this question is doing your research on what you should be paid by using sites like Payscale and Glassdoor. You’ll likely come up with a range, and we recommend stating the highest number in that range that applies, based on your experience, education, and skills. Then, make sure the hiring manager knows that you're flexible. You're communicating that you know your skills are valuable, but that you want the job and are willing to negotiate.
Even so, if you're asked, provide a sharp, on-point answer. Be clear and precise. If you're a great problem solver, don't just say that: Provide a few examples, pertinent to the opening, that prove you're a great problem solver. If you're an emotionally intelligent leader, don't just say that: Provide a few examples that prove you know how to answer the unasked question.
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).
"Choose an answer that shows that you can meet a stressful situation head-on in a productive, positive manner and let nothing stop you from accomplishing your goals," says McKee. A great approach is to talk through your go-to stress-reduction tactics (making the world's greatest to-do list, stopping to take 10 deep breaths), and then share an example of a stressful situation you navigated with ease.