Many of the best nonfiction writers violate punctuation rules frequently enough to indicate that the rules neither tell very well what to do nor inform very accurately about what is done. An examination of 18 prominent authors' use of the entire hierarchy of punctuation marks shows disagreement and inconsistency among the writers concerning application of rules. Analysis of the writers' works: (1) explains the differences among skilled writers as reasoned principle-based behavior; (2) produces a set of four principles that guide punctuation use; and (3) suggests that punctuation usage should be guided by principles of style, rather than rules that demand strict compliance. Teachers should encourage students to think of punctuation not as a matter of right and wrong, but in terms of stylistic concerns. Punctuation usage should be considered in terms of clarity, appropriateness, effectiveness, and taste. The "principle" approach is positive, while the "rule" approach is negative. In addition, the rule approach is intimidating for students, while the principle approach is easier to learn and less threatening. (Two tables, 122 examples, and 10 endnotes are included.) (SG)