To some extent, good testing procedure, like good language use, can be achieved through avoidance of errors. Almost any language-instruction program requires the preparation and administration of tests, and it is only to the extent that certain common testing mistakes have been avoided that such tests can be said to be worthwhile selection, diagnostic, or evaluation instruments. The list of common testing problems provided in this article is by no means exhaustive, but it has been drawn from wide experience with tests prepared for classroom and district use, and may therefore be said to be representative. It is intended as a kind of checklist to serve as a guideline for EFL teachers in the preparation of their own examinations. This article, originally published in 1982, is designed to help EFL teachers prepare effective selection, diagnostic, and evaluation instruments by avoiding common testing mistakes. Such mistakes are discussed under the categories of "general examination characteristics," "item characteristics," "test-validity concerns," and "administrative and scoring issues."