If you're a few years into your career in engineering, you've most likely already given some thought to seeking out a mid-level engineering job. In order to qualify for this vertical move, you need to be adept in the basics of production and design. At this point, you should have been documenting the products and processes you've participated in before seeking this new employment. You should be able to demonstrate a capability to analyze the process for continuous improvement and quality control. A potential employer will look for progress and development over your career thus far.