National discussions about source-based, academic writing in higher education have been and are increasingly tied to concerns about citation proficiency, plagiarism, and academic integrity. In response to these discussions, scholars have argued for better pedagogical strategies to teach students how to work with sources in effective and ethical ways. Since WAC graduate teaching assistants (TAs) work closely with student writers, they too need support in crafting these pedagogical tools. Based on quantitative and qualitative research, this article argues that the use of citation analysis heuristics in WAC TA professional development programs fosters metacognitive awareness and an improved understanding of source-based writing. This study of ten first-year graduate students at a U.S. research institution found that TAs who code their own academic writing developed an awareness and knowledge that influenced their development as both teachers and writers.