I went to Tate Modern with a friend and I observed the gallery in a very different way - instead of looking at the art, I began looking at the people looking at the art.
The space was packed and people negotiated around each other politely (mostly), almost queuing to see the next painting. I sat on a bench and waited for people to wander into my field of vision - I had to draw quickly as they didn't stay still for long. Some people stood folding their arms, some tilted their heads or gestured to their companion. A man squared up to the work, planting his feet far apart with his hands on his hips.
Some people listened to the audio guide while others took pictures on their phones.
People moved around the exhibition at a slow wandering pace and for the most part seemed unaware of the other visitors. They lingered at some works and just glanced at others.