This paper discusses a corpus-based approach to the generation of effective instructions. The approach advocated employs a detjiiled linguistic study of a corpus of a broad range of instructional texts to de- termine both the range of grammatical forms used in instructional text and the contexts in which they are vised. The forms that are consistently used by technical writers are taken to be the most effective. The results of this study are implemented in an auto- mated text generation system for instructional text. The primary focus of this study has been the use of rhetorical relations to effectively code actions and their procedural relationships in instructional text, but the approach can generally be applied to differ- ent linguistic issues and text genres.