"Word of mouth is the most powerful form of advertising! I gain a lot of business through existing, repeat clients who are happy with their travel experiences. I also leverage my own professional network, as well as social media platforms."

Asking this question the interviewer is testing what forms of advertising you are familiar with. The most obvious method in this technology age is social media and networking sites. One can also use high quality printing material like flyers and booklets advertising the agency and their products but that is not so popular these days when the internet can be accessed anywhere at any time in any Country. A well designed website promoting the agency and the latest deals is immediate and will reach the customers when they are relaxing and thinking about nice thing like booking a holiday of a life-time. Being at the right place at the right time is the best way to promote the most profitable sale.