In student assessment, teachers place the greatest weight on tests they have constructed themselves and have an equally great interest in the quality of those tests. To increase the validity of teacher-made tests, many item-writing rules-of-thumb are available in the literature, but few rules have been tested experimentally. In light of the paucity of empirical studies, the validity of any given guideline might best be established by relying on experts. This study analyzed twenty classroom assessment textbooks to identify a consensus list of item-writing rules. Forty rules for which there was agreement among textbook authors are presented. The rules address four different validity concerns-potentially confusing wording or ambiguous requirements, the problem of guessing, test-taking efficiency, and controlling for testwiseness.