The purpose of Study 1a was to determine the criteria that differentiate students who perform well and those who perform poorly on a standardized test of university-level writing. Discriminant function analysis revealed that measures of structure, sentencing, paragraphing, and grammar play the most important role in separating these two groups. These results were used in Study 1b to develop a tutorial attended by an independent group of students preparing to write a standardized writing exam. The intervention had a positive effect on their test performance. Participants reported the tutorial to be useful, committed fewer errors on most of the criteria, and had a higher probability of passing the exam. It was concluded that this type of tutorial is beneficial to students who are preparing for such exams and may have wider educational use for those seeking assistance with their writing skills.