The rapid population growth of under-represented minority groups and the continued under-utilisation of women mean that future growth in the domestic science, technology, engineering and mathematics (STEM) workforce is linked to greater diversity. Subject-matter mastery is important but insufficient for a student to pursue a STEM profession -- behavioural factors also play a significant role. We describe some of these factors and their relation to career choice, and provide recommendations for practitioners utilising them in STEM education programmes and projects. Understanding the behavioural components of the career decision-making process is critical to effectively engaging all students in the pursuit of STEM careers.