I have been taking a rather casual approach to what I type into the Edit Summary box when I finish editing a question, but I have started to think that may not be such a good idea. However, I really don't understand how these summaries fit into the long term scheme of things. I would like to get recommendations on what would be good practice for entries into Edit Summary.
My own current practice is mostly to use one of three stock phrases: "Improved formatting", "Made English more idiomatic" and "General cleanup". The first of these is one I use most and is a reasonably accurate brief description of a lot of my editing. It is the other two that I think might be dropped in favor of something better.