The cup should be full. He should look at it, so that his attention will not be diverted from it. However, if a great and prominent man is present, he should lead the grace. It is customary to let a mourner lead the grace, should all those present be of equal stature. Is is proper to convey the honor of leading the grace upon a person who is gracious, who hated unjust gain, and is generous with his money.
All holy matters require preparation.
The leader repeats this response. However, in other communities, it is not customary to respond in this fashion. In some communities, it is customary that this phrase be recited by the leader even when only three people recite grace together and G-d's name is mentioned. The latter practice is proper to follow. Those at the table should not recite this phrase.