Analyzing and understanding software developers' work habits and resulting needs is an essential prerequisite to improve software development practice. In this dissertation, we utilize different ... weiterlesenqualitative and quantitative research methods to empirically investigate three underexplored aspects of software development: First, we analyze how software developers use sketches and diagrams in their daily work and derive requirements for better tool support. Then, we explore to what degree developers copy code from the popular online platform Stack Overflow without adhering to license requirements and motivate why this behavior may lead to legal issues for affected open source software projects. Finally, we describe a novel theory of software development expertise and identify factors fostering or hindering the formation of such expertise. Our work supports researchers and practitioners in making data-informed decisions when developing new tools or improving processes related either to the specific work habits we studied or expertise development in general.