Firstly, have a week-to-view table that you can use to plan each placement day. You'll most likely be given dates and times where there'll be teaching so write those in immediately. Next, find out what clinics, theatres, other learning opportunities there are - find out when they happen and what time and then decide what you'd like to do. Fill your blank spaces with these. If you also do a sport/extracurricular activity on a regular basis, write those down.
I know this all sounds like common sense but I was surprised at how some of my fellow medical students hadn't even done something like this. Maybe I'm just obsessive about organisation but in medicine, I feel you have to be at least moderately organised to ensure that you get all your assessments done in a timely manner, etc.
Below are my weekly timetables; firstly in a blank notebook and secondly in my Hobonichi (which has been invaluable this year for keeping on top of things).