Finding optimal reaction conditions is usually complex, requires many experiments, and is therefore demanding in terms of human, financial, and environmental resources. This work provides a simple workflow for easier design of popular palladium-catalyzed C−H functionalization reactions, where the active palladium catalysts contain carboxylate ligands. The key factor for optimizing reaction conditions is to find a balance between two opposing effects of the carboxylic acid in the reaction mixture: generation of more reactive palladium catalyst versus deactivation of a substrate by its protonation.