We conducted a small-scale study to investigate if a brief timely intervention focusing on specific study strategies would improve student performance in university science courses. We targeted low-performing students after the first midterm exam in two courses (enrollments of 67 and 185) with different student populations, one with students in a very selective physics program and the other with a broad range of students in a general science elective course. In this intervention, instructors either met personally with students or sent them a personalized e-mail. Students who met with an instructor and discussed specific study strategies improved their performance from one exam to the next by up to 32 [plus or minus] 7%, without increasing their study time. These students also reported changing their study strategies during the term more than other students. Students who received an e-mail also improved their performance but not more than would be expected without an intervention. These results show that a focused discussion advising a small number of specific study strategies can have a large impact on the lowest-performing students in contexts in which the new study strategies are aligned with course structure, expectations, and assessments. This is in sharp contrast to results obtained from most general study-skills interventions. (Contains 1 table and 3 figures.)