Graphene quantum dots (GQDs) are promising luminescent materials for various light-emitting, biological, and energy applications due to their low toxicity compared to cadmium-based semiconductor quantum dots. The practical application and use of GQDs is driven by their luminescent characteristics. As such, a critical need exists to control and tailor the emission properties of these materials to suit the targeted optoelectronic applications. In this review, the fundamental properties, synthesis methods, and strategies for incorporating GQDs into optoelectronic devices are discussed. We present the fundamentals on luminescence mechanism of GQDs, including reflections on the defect-related properties (i.e., oxygen functional groups and odd-numbered carbon rings in the basal plane). We then offer new guidelines for the fabrication of GQDs aimed at increasing the luminescence efficiency. Finally, we introduce strategies for integrating GQDs into optoelectronic devices based on architectural design of the fundamental properties.