By the visual pattern, but mostly I'm guided entirely by my ear, what I hear.
Now, there are sometimes making a connection between one section and another that sometimes you do want to see the pattern because it helps you to lead into the next thing - it's a rhetorical thing, where you just see how the pattern has to go into the next thing.
Every time I'm a bit surprised always, what the patterns look like and what the whole thing looks like because, of course, I primarily hear.