Conceptual models are applied as the first step in software design methodologies for collecting the semantics involved in the universe of discourse. Nevertheless, the abstraction process creates some misunderstandings for novice designers, such as difficulties in modeling some constructs and in understanding the semantics that they represent. This paper presents a thorough study of errors detected among Database Design students in Computer Science Engineering when they apply the abstraction process to generate a conceptual schema using a specific model. Specifically, the paper focuses on errors made in the design of ternary relationships. Some heuristics are proposed in order to help novice designers avoid these common errors, and an experimental study is presented to compare the number of errors made by the students before and after applying these heuristics. (Contains 10 figures, 2 tables, and 3 footnotes.)