When choosing a shampoo for extensions, prioritize sulfate-free formulas. Sulfates are harsh detergents that can strip extensions of their natural oils, leading to dryness, tangling, and premature degradation of the hair. Opt for a gentle, hydrating shampoo specifically designed for dry or damaged hair. Look for moisturizing ingredients like argan oil, coconut oil, or aloe vera to replenish moisture and maintain the extensions' luster. Avoid shampoos with alcohol or silicone, as these can also dry out the hair or create build-up, making the extensions look dull and heavy. Always dilute the shampoo with water before applying it to the scalp and gently cleanse the hair in a downward motion to prevent tangling.