To achieve professional results, buyers must specify the color model (CMYK is standard for print) to avoid the color shifts associated with RGB files. The resolution should be at least 300 DPI at the final output size to prevent pixelation. Additionally, clarify the paper weight (GSM) and finish (glossy, matte, or UV coated), as these significantly impact ink absorption and the final visual appeal. For large-scale B2B orders, requesting a G7 Master Qualification or ISO 12647-2 compliance ensures consistent color reproduction across different print runs.