Undergraduates often struggle writing argumentative syntheses from conflicting sources. Written guides can help in the different phases of the process involved in these tasks and are more effective when accompanied by explicit instruction. Nevertheless, there are few studies on instructional rubrics as an aid to argumentative writing and none are focused on synthesis tasks. Our objectives were to compare (1) the effectiveness of a guide and a rubric as aids to the processes of selection and integration in writing an argumentative synthesis; (2) whether explicit instruction in synthesis writing strategies enhances the effects of both aids and (3) the effectiveness of the aids offered during the practice sessions performed with the support of aids and after removing those aids. The study was conducted with 120 undergraduate psychology students. An experimental inter/intra-subject factorial design 2 (Instruction) x 2 (Type of aid) x 4 (Time) was employed. We used mixed linear models to assess the intervention effects. The guide facilitated the selection of arguments. Both guide and rubric promoted integration. When students also received explicit instruction, the learning rate of integration strategies was accelerated, and the impact of guide and rubric was greater.