Going into a sub I next week. It'll be the first one of fourth year. Didn't get great experience presenting on our CL service during third year so really not sure what expectations are.
Inpatient, outpatient, CL, PHP? You're still generally less likely to present patients as a med student on most psych services, aside from maybe CL. The skill is in being able to discuss your patients in a cogent way.
That said, I agree with Nick that it's basically the same as other presentations except you are more likely to include social factors and your exam is a mental status.
For a generic answer:
10-15 minutes -- present everything (basically read your h+p), reserved mostly for exams and case presentations and sometimes includes extensive chart review, hospital course, collateral, developmental history, etc.
3-5 minutes -- Basically your H+P but you're sticking to the most relevant items for each section and may summarize. Likely to do this at rounds.
30 seconds - 2 minutes -- A skill you learn over time; discussing the patient as experienced doctors do, focusing on the most important aspects of the case. Often less structured, may weave between sections or omit sections of what you might find on an H+P. Relevant when staffing a relatively straightforward overnight case with an attending or asking for advice about how to approach a case when you don't have much time.
But as with most of these sorts of questions, the best answer is to ask a senior resident or your assigned attending what they expect.