The person leading the bentching at a sheva berachos recites the borei pri hagofen while holding the cup he held when he was bentching (cup # 1); the sheva berachos cup (cup # 2) is in front of him. He should have in mind that he is saying this berachah on behalf of the chosson and kallah and anyone else who wants to drink the wine. He drinks from his cup; he then pours from the second cup into the first; he then pours back from the first into the second. Some pour from both cups into a third, and then pour from that third cup into the first and second cups. The 2 cups are then passed to the chosson and kallah who drink from them. No berachah is made, unless they were not intending to be yotzei with the mevarech’s berachah. A sip is sufficient for them. The person who bentched must drink at least a cheekful, but should preferably drink a reviis, which would enable him to make a berachah acharonah.