As a PGY-3, I can say teaching medicine was far easier than teaching psych. I always reflected on teaching of residents/attendings when I was a student, and made mental notes of things I found helpful v. not helpful v. rude, etc. So when it came time to teach, I always started as such, especially in July.
1) Organizing your H&P - as this is our real building block in all of medicine, helping students in organizing this section is actually enjoyable. I also provide examples as I'm teaching, and tie this in as to how I personally would use this in beginning to formulate a differential diagnosis, that being said....
2) Differential diagnoses - with the data they collect, I would allow them to start to formulate THEIR DDx in a non-judgmental fashion. I would help them rank most likely to least likely, focusing on common things being common. I also helped them to think about a DDx in a different light. For example - taking a main symptom (in medicine for example, "Chest Pain" - and from their forming a broad ddx, then, incorporating history and physical exam components, +/- lab, imaging if available, to adjust how we would rank things, etc
3) Presenting - as students became more comfortable with these 2, their presenting skills also would improve. I would speak to them about projecting a sense of confidence in their presentations, going over their presentations before and after rounds, pointing the good, bad and in-between. For those where confidence was a primary issue, I made it a point to help boost that at different points (in rounds if they muttered the right answer to a question, I'd nudge them to speak up, get it right, receive some praise; sometimes I'd ask softer questions to those students, etc)
4) Treatment - not as common in the early part of the year, but I would also gauge their knowledge of this area. Looked to reinforce this either by taking them with me to see additional patients after rounds, encouraging them to go home to look up "what happens if complication X, Y, Z arose and I was the only member of the team and I HAD to do something on my own (even though this obviously would never happen)" - I would do things like when they tagged along to help increase their curiosity to learn, make them a more active member
Remember, you have something to teach, even if you don't realize it. You're not going to get a lot of knowledge type questions, especially early on. Focus on helping them build a foundation. Psych is a little more grey, but you can still focus on the basics. Hope this was a little bit helpful. This is how I did a lot of my medicine months. Adapted of course for psych portion of teaching