It would appear that "practical criticism" asks for the reader's unclouded, unbiased, emotionally pure response to reading something.
This "discipline" began in the 1920s under the guidance of I.A. Richards of the University of Cambridge. He began an experiment by giving students poems without any referents: in other words, he did not provide an author's name or even the date the poem was written. Richards' purpose, and ultimately the results he achieved are summarized as follows—he wanted fresh, emotional responses to literary works the students read:
For Richards this form of close analysis of anonymous poems was ultimately intended to have psychological benefits for the students: by responding to all the currents of emotion and meaning in the poems and passages of prose which they read the students were to achieve what Richards called an 'organised response'. This meant that they would clarify the various currents of thought in the poem and achieve a corresponding clarification of their own emotions.
The use of "practical criticism" seems very different today than when Richards first introduced it. In today's classroom, it seems more a method of measuring what a student knows, rather than being used in its purest, most original form.
[Practical criticism] is a part of many examinations in literature at almost all levels, and is used to test students' responsiveness to what they read, as well as their knowledge of verse forms and of the technical language for describing the way poems create their effects.
The intent Richards originally had, I believe, is where this discipline has the most value. Reviewing what one knows is not nearly as meaningful to the reader as discovering what he or she thinks.
So if I were to write something on "practical criticism" I would reflect on its original intent and how it is used today. Then I would go further. I would have a friend, teacher, or librarian find an obscure poem (or piece of prose) for me. I would read it without knowing who wrote it, why or when, and respond to it on a personal level. I would then have the person who supplied the poem give me all the information available, I would respond to the poem again, and then compare and contrast my two responses. At this point I would reflect personally on the difference between the two readings, pointing out what changed, what did not, and which experience was most meaningful and why.
This "experiment" could also be done with a friend or two who are committed to keeping their work in line with the spirit of the exercise, who would take it seriously and respond honestly, with energy for the task and a commitment to its purpose...to help me with my "project."
As an educator, we are always trying to find ways to make information meaningful so our students find a connection to it. Richards (it seems to me) was doing the same thing. He wanted to open minds, let them go where they would, and generate responses that were pure and honest. "Practical criticism" has much more value, in my opinion, when used this way than when used as a testing or measuring device of a student's knowledge—when all creativity seems to be lost, replaced by a need to qualify and quantify the various aspects of poetry.
If I were given this essay, the above "experiment" is how I would respond—on a personal, more meaningful level.