A professional factory should offer OEM/ODM services with a dedicated laboratory. Evaluate their ability to provide custom formulations (e.g., anti-dandruff, color-safe, or organic). Request information on their stability testing protocols, which should include centrifuge tests, heat cycles, and light exposure tests to ensure the shampoo doesn't separate or change color over its shelf life. Top-tier manufacturers on Made-in-China.com often provide packaging design services, including silk-screen printing and custom bottle molding.