When sourcing perfume, the concentration of fragrance oils is the primary indicator of quality and longevity. Parfum (20-30%) and Eau de Parfum (15-20%) offer the longest wear time, while Eau de Toilette (5-15%) is more suitable for daily, lighter use. You must verify the olfactory pyramid (top, middle, and base notes) to ensure the scent profile matches the brand's original intent. Additionally, check the clarity of the liquid; high-quality perfume should be free of sediment and cloudiness, indicating proper maceration and filtration processes.