The whole point of résumés and cover letters is to sell your skills. Rather than simply listing the responsibilities in the positions you’ve held (as many candidates do), call out specific ways you’ve made a difference in those roles. Suppose you’re in sales: Did you exceed your annual targets? By what percentage? Or, if you’re a customer service manager, did you reduce the number of complaint calls? How did you do it — and by how much? Quantify whatever achievements you can, and include promotions and other acknowledgments of your success. For example, you may have started as a production manager and then, after six months, taken on full control of the firm’s quality assurance program. Mention accomplishments like that — they reflect the trust you earned and your level of competence.
Adapted from the HBR Guide to Getting the Right Job.