At the top of my record book, I always write just' left outer leg high, left middle leg high, left middle outer leg, left middle, middle, leg . I will use one leg and can normally (if sets are ok) use one leg for about 12 sets, then the other, then my left or right bum- then I write upper, outer etc...same as i do for my legs.
I find my stomach just too painful to use on a regular basis, as I keep getting pains from the sets anywhere from immediately to 24 hours after i have put the sets in). It can take me up to 5-6 weeks before I have to go back to the same areas.
I also write down cartridge change days as well. Always writing down if I have to change sets....the worst time 4 times on one day!!!! And each time I write down where they have been changed to etc...as by the time I have tried a set in my leg say twice and had problems twice I will move to my bum.
Other than that I would get a blank photocopy of a body chart from hospital and mark on the chart where the sets go, but I don't do this, as it is another faffing around minimum of every two days. I don't want to make things too complex to remember...