Another stylistic post.
Some writers write things like, "The cat licked her shoulder, then looked unconcerned."
The proper way to do it is: "The cat licked her shoulder, and then looked unconcerned."
I don't change "then" to "and then" if the writer has written it that way. My preference is just "then," even if it isn't in the style books. I like to trim out words that don't have to be there. It makes for a smoother read.
I look for what the author uses and make it consistent throughout the manuscript.