It goes a little like this: I sit down and I start thinking about what I have to do when I finish meditating. That thought engenders new thoughts about someone I'm in an argument with, and then I start to explain to myself why she is wrong and I am right, and I'm far down this road when I remember I'm meditating and I notice that I'm breathing. And I think, I'm spending an awful lot of time thinking about this, which thought might send me off thinking about how hopeless I am at meditation and what time is it anyway? And then I notice I'm still there, still breathing. Meditation has a lot of this returning. And each time I return, my thoughts get a little softer, my beliefs about the world a little less real or at least less urgent.
When I meditate and I notice I've gone somewhere, and it's not somewhere I want to be (these clouds of thinking start to be painful after awhile) I come back to my body, to a sensation. I notice I'm breathing, I'm heavy into the chair, I can feel my hands. My mind softens. Then I remember my koan, which is a piece of text like a line from a poem. "The coin that's lost in the river is found in the river." That's all. Repeat as necessary.