Cf. Siddur, p. 268ff.

Whenever Birkas Kohanim is said, the procedure to be followed by each congregant is as follows.1 When the Kohanim say יברכך the congregant faces forward; when they say wה he turns his head to the right, i.e., to the left of the Kohanim; at וישמרך he faces forward; at יאר he faces left; and so on, [word by word — center, right, center, left, etc.,] until when they say שלום he faces forward.2

The prayer beginning רבונו של עולם is said only while the Kohanim sing; when they say the words of the blessing, one should listen. When they sing the melody that introduces the third-last word, וישם, the congregation says from רבונו של עולם until הצדיק; while they sing the melody for לך, the congregation says from ואם to אלישע; while they sing the melody for שלום, the congregation says from וכשם to לטובה; and while they say שלום, the congregation says ותשמרני ותחנני ותרצני.

One says the paragraph beginning אדיר במרום after having responded טמן to the blessing, and while the tallis still covers one’s face.

When the Kohanim utter the Divine Name, the congregation does not respond ברוך הוא וברוך שמו; nor do they respond כן יהי רצון [at the end of each of the three phrases]; nor do they say בזכות אברהם אבינו, יצחק אבינו, יעקב אבינו.

The paragraph beginning רבונו של עולם is said once only.