First is preparation, -- What are your strengths, How do you align with the job description? More importantly, how do you stand out? Before the interview , try to formulate your answer by researching the company and understanding the job description, what is unique about you that makes you qualified.
Most often this question comes later in the interview. If this is the case ,you have had the opportunity to find out what qualities are important to the hiring manager, I advise my clients to ask this question early the interviewing process. What's important to the person doing the hiring? With this knowledge you can provide an answer that is tailored specifically to the job.
Doing so will make you unique and stand out from the other candidates interviewing for the job.