הלכה אויף משלי 22:9

If all those who are part of the group are of equal status and there is a kohein among the group it is a mitzvah to honor him with leading the Birkas Hamazon, as it is said:⁵Leviticus 21: 8. "You should sanctify him." But if there is a great Torah scholar in the group, he should lead the Birkas Hamazon. It is customary to have a mourner lead the Birkas Hamazon. This applies only when they are of equal status. It is also proper to honor with the leading of Birkas Hamazon, one who is generous, who despises illegal profits, and dispenses charity with his money, as it is written:⁶Proverbs 22: 9. "One who is generous shall be blessed." Do not read yevorach—"shall be blessed," but, rather, yevareich—"shall bless."

After that the meal begins. It is proper to eat the entire meal²⁹Nevertheless, if you reclined only while eating the matzah and drinking the Four Cups of wine, you have fulfilled your obligation. (Ibid. 472:23) while reclining It is customary to eat eggs. It is wise to use good judgment, and not overeat, so that you will be able to eat the afikoman, as required, (with appetite), and not on a full stomach.³⁰If you are so full that any more eating is abhorent, and you eat the Afikoman in such a condition, you have not fulfilled your obligation. (Ibid. 476:6) Roast meat should not be eaten, on the two seder nights, not even roast poultry. Even if it was boiled and then pot roasted, it should not be eaten. Some have the custom not to eat any food dipped in liquid, on the seder nights, except the two required dipped foods, so that it should be prominently recognized that these two are mitzvos. After completing the meal, the afikoman is eaten³¹Women are also obligated to eat the afikoman. (Ibid. 476:2) to remind us of the Pesach sacrifice,³²Since it is a reminder of the Pesach sacrifice, it must be eaten before midnight, as was required of the actual Pesach sacrifice. (Ibid. 476:6) Midnight does not mean 12 P.M., but is dependent on the length of the hours of daylight and night time. which was eaten at the end of the meal so that you should be completely satiated. It is proper to eat two kazeisim (of matzah for the afikoman), one to remind us of the Pesach sacrifice, and the other to recall the matzah that was eaten with the korban Pesach . At any rate, you should not eat less than a kazayis, and you should eat the afikoman, while reclining. After eating the afikoman, it is forbidden to eat anything.³³Our Sages ordained this rule, so that the taste of matzo remains with you. If you forgot and did eat something else, you must eat another kazayis of matzo for the afikoman. (Ibid. 476:1) ³⁴You are permitted to drink water. Some Poskim also permit tea. Other drinks, however, that are tasty or sharp, that would remove the taste of matzah are forbidden. (Ibid. 478:2, 481:1) The third cup is then filled for Birkas Hamazon. You must make sure that it is clean, not containing leftover wine, that is to say, nothing is left from the wine, in which matzah may have been soaked during the meal. If it is not clean, it requires washing and rinsing (See Chapter 45:4 above). It is a mitzvah to make an effort to recite Birkas Hamazon with zimun (three males), but you should not go from house to house to look for people required for zimun, because each person is required to say Birkas Hamazon in the place where he has eaten. It is customary for the master of the house to lead the zimun³⁵He takes precedence even over a guest, who is usually accorded the privilege of leading the zimun. (Ibid. 479:13) as it is said: "A man of a good eye shall bless," (Proverbs 22:9) (see Ch. 45:5) and he is called, "A man of good eye," (i.e. a generous person) because he said: "All who are hungry—let them come and eat" etc. After Birkas Hamazon, the berachah is said over the third cup, and you should drink it while reclining. It is forbidden to drink between this cup and the fourth cup.

Grace After Meals on the Third Cup. Contains one section:
After eating the afikoman, we mix the third cup and bless the Grace After Meals and Creator of the fruits of the vine upon it, then one drinks it while reclining. And one neither blesses a post-consumption blessing upon this third cup, nor should one drink wine between the third cup and the fourth cup. Rema: However, one is able to drink many times from the third cup and all of it is considered as one drinking, even though one interrupts between these drinkings (Maharil, Maharai, and Tashbetz). It is a mitzvah to repeat after the zimun. Rema: And the greatest among them says "Hodu" and "Ana" and the others respond after him (Kol Bo). And the greatest may give permission to a younger person (Maharil). And one may join the zimun for the purpose of Hallel even though he did not eat with them. And the custom is that the homeowner recites the Grace After Meals on Passover night, as it is said, "He who has a good eye shall be blessed" – and he is called "good eyed" since he said "Let all who are hungry come and eat," etc.