Before walking through under a Torii (an archway to a Shinto shrine) after arriving at a shrine, visitors are supposed to perform 'Isson' (deeply bowing at forty-five degrees) in front of the Torii.
神社に到着し、鳥居をくぐる際は「一揖（身体を45度折り曲げる会釈）」するのが望ましい。