Admittedly, my research group is large. Often, large research groups will begin to have a hierarchical structure where the PI manages the post-docs who manage the PhD students who manage the undergrads. I deviate from this strategy. I feel that the only way I can truly know what is going on in my group is by interacting with everyone individually.
My approach to my research group management style is directly related to my approach to student mentoring, as the two are inter-twined. I meet with every student bimonthly, individually for 30 minutes, in addition to weekly group meetings (1hr). Depending on the stage of the student’s academic career, the meetings can include discussions on coursework, research and personal career goals. By meeting at least every other week, research challenges are addressed as they arise and personal issues are brought to my attention.
In addition, we have yearly reviews that are comprised of two stages: 1) a self-evaluation and a 2) formal evaluation (I fill out). Then, we meet to discuss. These reviews provide an opportunity to discuss a student's or post-doc's progress in research or their degree program as well as any strengths or weaknesses.
However, these bimonthly meetings are a minimum. I strongly believe in an open-door policy, which enabled by the fact that my office is across the hall from my research labs and near my student offices.
My undergraduate, graduate, and post-doc students have obtained industry positions in a wide range of fields, including the semiconductor industry, electronics, and instrumentation fields. Additionally, I have placed undergraduate students in top PhD programs and post-docs in faculty positions. A complete list is located on the group alums page.
Currently (May 2016), the average time is approximately 5 years. Based on an analysis of my current senior graduate student's progress in their PhD research, it will probably stay in this range (5 years) for at least the next few years. However, it is important to note that this number is primarily dependent on the student. In other words, I do not have a minimum or a maximum number in mind.
The majority of my PhD students are supported on some form of a PhD fellowship (internal USC or external) for a portion of their PhD. For the remainder of their PhD, I support them on my government, foundation, or industry contracts. However, I do expect students to TA for 1 year. This expectation is motivated by two factors. First, TAing is a good experience. You learn how to clearly explain concepts and give presentations. (And you become confortable giving presentations). If you are planning a career either in industry or in academia, you will need to be able to give presentations and explain your work. So either way, this experience is useful. Second, if you are planning a career in academia, TA experience is expected. Additionally, if you TA and discover you don't like working with students, it is better to discover this fact early. Similarly, the converse can be true.
While previous research experience is important, many skills are translatable. As such, the specific field is not as important as the fact that a student performed research successfully. It is also important to remember that admissions decisions consider numerous factors, not just the field of prior research. Additional information is located on this webpage.
One of the key benefits of my group is that it is a virtual melting-pot of talents. I actively recruit from a wide range of disciplines, and no one joins the group knowing everything. It simply is not possible. Everyone works together and teaches each other. I strongly feel that the point of graduate school is both to deepen your knowledge in one field and expand your skillset into another. If you don't push yourself and get outside of your comfort zone, you are doing something wrong.
My main goal in choosing PhD students is to find smart, talented students who are not afraid to try something new and who work well on an interdisciplinary team. In my group, students with different academic backgrounds need to work together. This type of collaboration is very different from working within a single field. As such, I typically involve my current students/post-docs in the new student selection process.