Look at the signature and seal, look at the style of painting, look at the details.

1. Look at the signature and seal: Huang Yongyu's paintings all have his signature and seal. The signature and seal look vague or irregular and are forged.

2. Look at the painting style: Huang Yongyu's painting style is unique and has strong personal characteristics. The style of this painting is quite different from his other works and needs further appraisal.

3. Look at the details: Huang Yongyu's paintings are very meticulous in details, and the details in the paintings look rough or unnatural and are forged.