This study aimed to discover the insight of error correction by implementing two correction systems on three Iranian university students. The three students were invited to write four in-class essays throughout the semester, in which their verb errors and individual-selected errors were corrected using the Code Correction System and the Individual Correction System. At the end of the study, the studentsí change of verb errors and individual errors from the first to the last in-class essays were calculated to examine the effectiveness of the two correction systems in this study. Moreover, to uncover the studentsí perceptions and opinions toward the two correction systems, three researcher student conferences were conducted each time after the correction. The findings of this study suggested that (1) Conferences are important for students to clarify confusing ideas and enhance their interaction with the teacher and their errors. It is recommended to be used in error correction to make the correction procedure a two-direction communication; (2) Learner-centered correction in which the control rests on learners may contribute to learnersí autonomy of learning and intrinsic motivation, and may further result in the effectiveness of error correction; (3) While correcting studentsí errors, teachers may need to pay more attention to less-advanced students, as they may need more help and may benefit much from the correction; (4) The better way to solve Iranian university studentsí problem in using English tenses may be to expose them to more authentic English, but not in over-simplified rules; and (5) Teachers should avoid putting answers directly on studentsí written errors, but adopt more implicit error identification techniques for students to reflect on their own errors.