Here lies the single most critical nuance of French social interaction: please is entirely useless without hello.
In English-speaking retail and service cultures, stepping up to a counter and immediately saying, "A croissant, please," is considered efficient and reasonably polite. In France, that exact interaction is perceived as hostile. By skipping the greeting, you treat the person serving you as a transaction machine rather than a human being.
In French social theory, every commercial exchange begins with a mutual acknowledgment of existence. Before you ask for directions, request a table, or ask the price of fruit at an open market, you must look the clerk in the eye and say bonjour (or bonsoir after approximately 5:00 PM). Only after they return the greeting can you present your request accompanied by s'il vous plaît. Skipping bonjour renders any subsequent s'il vous plaît completely meaningless.
