The situation is a common one for me: classroom, instructor, students--find an interesting photo. I've been here a hundred times. Here is how I solved it this time. From the metadata I can see that I was in the room for 15 minutes, and I shot 75 frames.
What I look for is interaction. In this case, students are in small groups, and the professor is visiting each group in turn. I follow him, and put him at ease thusly, “If it looks like I'm stalking you, it's because I am.” “I figured as much,” he says.
Walking into a situation wearing two honking big cameras gives you a lot of social authority. Different situations, of course, require different behavior. Sometimes I need to remain discrete (for say, a law school lecture). In this case, I roam the room pretty much like I own it, though with my antennae up. If I feel the hint of discomfort or awkwardness from someone I back off. Or I face it. “Yes, this is really awkward isn't it,” I'll say. And I'll share the experience of feeling awkward with them. Now we're connected, and I have permission, or I have a clear boundary to respect, one or the other.
This class was informal, so, as I frequently do, I made a spectacle of myself. I stand on top of tables. I crawl on the floor. I'm a little guy, and I'm limber, which is a tremendous advantage in squeezing into tight quarters. That, and with the cameras, I become a highly visible, and thus normal occurrence in the room. It's amazing how easy it is to disappear by being the most obvious presence in the environment.
I was starting to put a photograph together. Basically, one of two angles was working, low or high. With everyone packed in so tight, it was easier to isolate elements if I worked low. With each group I visited I learned a little more about what was working. By the time I got to this gang, I pretty much knew what the photograph I was after looked like.
I had solved the technical issues by this point too. I nailed down an ISO (3200) and an exposure, 1/20 f/9, (set manually, via histogram) to maintain depth of field. With IS, I knew this was a safe shutter speed for me to handhold. The limiting factor would be subject movement.
I set up the composition, though I can't say that I was doing so with much conscious intent. Looking at the result I can see that I was lining up the woman's arm on the right to be parallel with the frame edge, and letting the diagonals of the desk and the other figures drive my eye around the frame (if you look at the sequence, you can see that I tried a couple with a level horizon. I apparently didn't like it.). The framing happens unconsciously. What I am consciously managing is the action. I'm micro-adjusting the framing so that I can see everyone's face. I'm watching for when they are all engaged at once. I'm monitoring the gestures of the professor. I fire the shutter every time it feels like everything is more or less coherent. Every time it feels close, I take a picture. At some point, I know it's in the can.
I have not looked at the LCD screen once during this entire sequence. As soon as you start assessing what you've shot, you are no longer connected with the moment. Save it for the end of the day.