Take each criterion and define just what you mean. Although you'll see many sample rubrics with abstract or general terms in the criteria column, the best rubrics draw on shared knowledge about key features of writing. If you've talked with students in class about what you mean by "demonstrated understanding," then you may not need to define the term in your rubric. But if you can help students by providing a gist of what you mean by a concept, use your rubric to do so. You'll also find that by defining terms, you'll clarify in your own mind what's most important to comment on.
For example, sometimes teachers think that "organization" is a key criterion. But what they mean is not whether students use appropriate headings (adequate for their understanding of organization) but how well students help readers move through the paper as a whole, and that movement might be helped by headings in addition to transitions, repetition of key terms, forecast maps, and other devices that create coherence for readers.
Thus, defining criteria can help you refine your overall list of criteria and can help make assessment of papers easier and faster.