This study was conducted to find out the effectiveness of my writing instruction and prepare for the following writing instruction in a university context in the Southern part of South Korea. To achieve the goal, three research questions were raised and answered in a given order; 1) Participants of the study did not show progress in writing in terms of accuracy and fluency, 2) The most frequently appearing errors showed their own hierarchical order, such as sentence types and meaning > mechanics > word choice > agreement > main verb > article, and 3) agreement > main verb > mechanics > sentence types > usage errors were survived at the end of the semester. Based upon the findings of the study, instructional intervention including writing can be inevitable. As for the solution, these errors were categorized suitable for the format of quizzes.