This article describes significant improvements in the methods for expressing exogenous genes in *Drosophila melanogaster* at defined levels and in spatially and temporally controlled patterns. The authors systematically varied core promoters, UTRs, operator sequences, and transcriptional activating domains used with the GAL4, LexA, and Split GAL4 transcription factors, as well as the GAL80 transcriptional repressor. They used site-specific integration to make quantitative comparisons between different constructs inserted at the same genomic location. Additionally, they characterized a set of PhiC31 integration sites for their ability to support transgene expression in the nervous system. The optimized reagents overcome previous limitations, enabling more complex and sophisticated genetic manipulations. The modular vector backbone allows for further improvements and the addition of enhancer fragments in a reproducible orientation. These advancements maximize the consistency and predictability of expression patterns.This article describes significant improvements in the methods for expressing exogenous genes in *Drosophila melanogaster* at defined levels and in spatially and temporally controlled patterns. The authors systematically varied core promoters, UTRs, operator sequences, and transcriptional activating domains used with the GAL4, LexA, and Split GAL4 transcription factors, as well as the GAL80 transcriptional repressor. They used site-specific integration to make quantitative comparisons between different constructs inserted at the same genomic location. Additionally, they characterized a set of PhiC31 integration sites for their ability to support transgene expression in the nervous system. The optimized reagents overcome previous limitations, enabling more complex and sophisticated genetic manipulations. The modular vector backbone allows for further improvements and the addition of enhancer fragments in a reproducible orientation. These advancements maximize the consistency and predictability of expression patterns.