The research aims to investigate common mistakes in students' paragraph writing and then suggest some solutions to overcome and enhance students' writing skills. Both quantitative and qualitative methods were employed. Mistakes in the paragraph writing of 60 first-year students were gathered and analyzed. The research results reveal a total of 435 mistakes categorized into three groups: grammar, vocabulary, coherence and four main error causes including grammar and vocabulary weakness, lack of wrtiting practice, Vietnamese interference, and infrequent feedback and correction. Through the findings, several suitable measures have been proposed to assist students in self-correcting their writing mistakes and improving writing skills more effectively. Simultaneously, these measures aim to enhance the effectiveness of teaching writing skills for instructors.