Just read the Critical Thinking readings. It's an interesting read and has several helpful points. I found the page Questions Using Elements of Thought to especially useful. It's a good check list to consider when creating art.
There's so much to consider when a person creates anything. There are points mentioned that I wouldn't normally think of as well, such as the artist's "assumptions" and "implications." It's good to remember these for the next crit.
I find it hard to vocalize ideas in crits a lot of the time. Hopefully I can become a "Master Thinker" one day like the text describes. Haha.