294. Bentching
44:6 Bentching is recited sitting, not standing or walking. Even if one ate while walking around his house, or standing or reclining, he should sit when it’s time to bentch. (If one ate while walking on the road, he need not sit – OC 183:11.) Reclining while bentching is considered arrogant. One should wear outer garments and cover his head (hence the practice of many to wear a hat and jacket for bentching – MB 183:11), and he should not do anything else while bentching, in order to have proper reverence.
44:7 The practice is for those who hear someone bentching to respond “Amen” to each phrase that begins “HaRachaman” (“May the Merciful One…”). This is based on a Midrash to the effect that when one hears a person pray or bless Israel, he should say Amen even if God's Name was not mentioned.