As an July 1 intern teaching a July 1 3rd year med student, you want to focus teaching the med student the "system": how does the hospital run, how do rounds work, what the med students' job is in terms of data collection and following up. You want to teach them proper presentation skills with focus on understanding what is significant, what is relevant but not significant, and what is irrelevant and insignificant. Since this will be their first rotation, you want to teach them good habits (organization, professionalism, team work) and get them on the right foot.
As a July 1 intern teaching a July 1 4th year medical student, you want to focus on teaching that student how to manage the panel of patients you are following (5 or more patients), and have them be more responsible for the day-to-day tracking of labs, meds, and "time" (how long post-op, what day of antibiotics, how long have lines been in, how long has Foley been in). And as you (the intern) learn more about how to come up with your own assessment and plan, you partner up with the 4th year and learn that together. Your 4th year is likely to be a sub-I, so you want to train them on the paperwork/scut/coordination, but also on recognizing and acting on emergent/life-threatening conditions. When you are teaching, you need to focus on formulation of differential diagnosis and how to move them up or down based on information you have/don't have. You also want to teach them things you've learned through your entire internship, and have them challenge you with questions so that you both can look them up and expand both of your knowledge bases (use teaching as an opportunity to learn.)
As a June 1 intern teaching a June 1 3rd year medical student, the intern already understands how things work and now you need to focus on accurate data collection and interpretation, recognizing and acting on life threatening/emergent conditions, and managing the active disease process. The medical student, however, will be new to your rotation, so you want to still focus on how to do a good presentation on your service with the patients you're dealing with, but at this point, you have a basis for comparison with other services. So your job now, is to help them "connect the dots". Compare 2-3 patients with similar diseases and talk about how management is the same/different. Compare a patient on your service and compare it against another patient seen on a different specialty (pediatrics, OB, surgery, whatever) and talk about similarities and differences.
A June 1 intern teaching a June 1 4th year student should focus on... forget it. They're not paying attention.