This study investigated the possibility of categorizing writing strategies of undergraduate students and instructing them in terms of their categorization. Based on the questionnaires of eighty-four undergraduate students, ten students were collected by stratified sampling to obtain more detailed information about their writing processes; written outputs and self-reports of the remaining seventy-four students were also collected. Data analysis was performed by both qualitative and quantitative methods. As a result, the writing strategies of the undergraduate students were categorized into four levels, in terms of a level of dependence on preplanning. In addition, it was assumed that the less a student depended on preplanning, the more he or she depended on revision. Therefore, the final categorization turned out to be either plan-oriented or revision-oriented; the previous four levels were then named as strong plan-oriented, weak plan-oriented, weak revision-oriented, and strong revision-oriented, respectively. Writing strategy categorization had no meaningful relationship with text quality according to the simple regression analysis; thus, these four categories could be admitted as valid categories. Writing instruction in terms of categorization was also proposed, based on the analysis of the strengths and weaknesses in each category.