Zhāopìn shí yào zǐxì shěnchá, fángzhǐ yú mù hùn zhū.
Vet candidates carefully when hiring, to keep imposters out.
Tips
history
From Wei Boyang's 《参同契》 (Eastern Han alchemical text): 'how can fish eyes be pearls?' — a meditation on distinguishing the real from the false. The four-character idiom condensed from the line.
memory
A round, white fish eye looks just enough like a pearl to fool a careless buyer. The image captures every counterfeit-vs-genuine situation perfectly.