After eating the Afikoman, everyone at the Seder washes Mayim Aharonim, and then Birkat Ha’mazon is recited over a cup of wine. The cup must be rinsed – both the interior and the exterior – before Birkat Ha’mazon, even if it is clean. The one leading Birkat Ha’mazon is handed the cup, which he takes with both hands and then holds with only his right hand throughout the recitation of Birkat Ha’mazon. He should preferably hold the cup at least one Tefah (3-4 inches) above the table, and look at the cup while reciting Birkat Ha’mazon.
One must recite Birkat Ha’mazon with Kavana (concentration), and remember to add Ya’aleh Ve’yabo. One does not perform Heseba (leaning) during Birkat Ha’mazon, as this would not be respectful to the Beracha. Immediately after completing Birkat Ha’mazon, one recites the Beracha of "Boreh Peri Ha’gefen" and drinks the cup of wine while leaning on the left side. If one drinks without Heseba, he must pour another cup and drink again while leaning.
One may not drink wine in between the third and fourth cups of wine at the Seder. Therefore, if a Hatan is present and Sheba Berachot are being recited, only a single cup of wine is used for the Sheba Berachot (as opposed to other times, when, depending on the circumstances, two cups are used). This applies regardless of whether two or seven of the Sheba Berachot are being recited. (The issue of how many Berachot are recited under which circumstances lies beyond the scope of our discussion here.) The Beracha of "Boreh Peri Ha’gefen" is recited first, immediately after Birkat Ha’mazon, followed by the Birkat Hatanim, and, of course, the wine must be drunk while leaning. This Halacha is mentioned in Yalkut Yosef (p. 345; listen to audio recording for precise citation).
