This paper reviews research about writing that may inform teachers' observations of their students and their decisions about how best to support students' efforts. First, since ways of using written language vary with different social situations, the paper reviews research on how literacy functions in varied communities, including both the classroom and the larger community the student inhabits outside the classroom. Second, since writing is a complex process, one involving the orchestration of many kinds of skills, the paper reviews research on the composing process, with the intent of supporting teachers' efforts to observe individual writers' ways of composing, including their successes and challenges, and thus help writers overcome difficulties that cannot be seen on the page, ward off problems before they occur in print, and ease students' ways into writing. Third, since writing is a developmental process, one in which today's ways of composing change in complex ways into tomorrow's, the paper reviews research on the development of writing, on the assumption that such knowledge may help teachers appreciate the signs of progress that may be hidden amidst students' sighs and scratch-outs, and see the kinds of support individual students might find most helpful. One figure is included, and 19 pages of references are attached. (SR)