Most teachers around here do leave seating charts for subs. It makes things so much easier. I have names to go with miscreants. But sometimes, the teachers don't leave me a seating chart. That's when I make one of my own.
It's simple enough. I make grids to carry with me for just such an eventuality. I found that a simple 7 x 9 grid covers most classroom configurations. If it's a strange setup, I just cross off boxes I don't need. If it's a simple row-like setup, I can fold the thing in half and use it for two periods.
Several years ago, I was called to cover an English class. What I ended up with was a strange little setup. There were three 8th grade teachers (an English teacher, a math teacher, and a history teacher) who had a team thing going. For three periods, they traded off three classes. These three classes were going on a field trip, but some students weren't going to be allowed to go.
Another sub and I split those not going into two groups. I ended up with about 15 students. I made a seating chart of those who were with me, and for the three hours that I had them, I was able to keep pretty good tabs on them.
After a short time, I didn't really need the seating chart. My own seating chart was more vital another time.
A few years ago, the English teachers were going to be out periodically for a curriculum meeting thing. I got all the dates of a 7th grade core teacher (she had them for two periods of English and world history). This particular teacher never has a seating chart because she is constantly changing the seating arrangement.
She's pretty famous at the school for being a strict teacher. I had subbed for her before, so I knew the seating chart issue. I came prepared.
That first day, as I called roll, I wrote a seating chart for myself. Usually, when I do this, I leave the seating chart for the teacher so he/she knows where the students sat, just in case they were doing something they weren't supposed to. This time, I took the seating charts home with me, and I typed them out on the computer.
The next time I covered that class (almost two weeks later), I brought my seating charts. I called roll again, and I changed those students who had been moved since the last time. Less than a dozen students were in different seats, and it was easy enough for me to fix this on my seating chart.
Within five days in this class (over a period of about two months) I learned many of their names. And those I didn't know, I had that seating chart that I updated every time I was in the class. It made discipline that much easier to handle.
I ran into those students in other classes through the years. It was interesting to see who ended up at the continuation high school versus those who ended up in AP classes. I won't be seeing them anymore. They all just graduated.