Lots of good advice on here. When I was younger and interviewing to consider switching jobs every couple of years, there was one phrase that I would always work into the conversation. After demonstrating that I was familiar with the company and industry and how I would fit at the new job, I always told to my potential bosses and colleagues that besides understanding how to do the work, above all "my job is to make your job easier." That always conveyed confidence, competence, and being a team player.