As Internet resources for assignments become increasingly accessible to university students, the risk that students will misattribute this material and plagiarise it is also on the rise. To address this concern, we trialled several strategies to reduce the incidence of plagiarism and to improve writing and referencing among first-year psychology students across 10 consecutive semesters. Each semester's cohort ranged in size from 950 to 2,000 students. These strategies included the sole use of plagiarism software as a deterrent; several interactive writing and referencing exercises with feedback; and mastery quizzes on writing and referencing. The findings revealed that the most significant reduction in reported plagiarism cases occurred between the ‘no education (a deterrent-only) strategy’ and when a writing exercise with feedback strategy was introduced in the following year. Different patterns in the reduction and spread of various kinds of plagiarism cases are also discussed.