Mentoring is a key part of career development, especially in emerging fields such as social entrepreneurship. Internet technologies have made it easier for novice social entrepreneurs to identify and connect with mentors online. Yet, we do not know the strategies mentors use to advise professionals navigating emerging fields. Knowing these strategies would allow us to create technologies for more effective career mentoring. This paper presents an expert model of career mentoring for novice social entrepreneurs. To build the model, we conducted a retrospective cognitive task analysis with 9 mentors who have at least 5 years of experience advising novice social entrepreneurs. We found that mentors help novice social entrepreneurs regulate career-related stress and make decisions about next career steps. Our findings suggest that further exploration of career mentoring strategies might allow designers to develop technologies based on the expert model, such as intelligent agents, to support and scale mentorship in emerging fields.