Shulchan Aruch, Orach Chaim 167 שולחן ערוך, אורח חיים קס״ז

One breaks the bread at the place where it baked well. The Rema adds: with our bread, one should break at the side of the loaf and cut a little from the upper and the lower side. He cuts the piece of the breaking, and he must cut only a little, so that if he holds the piece, the rest of the loaf rises with it; for if not, it is considered a piece. He leaves it attached to the loaf and begins the blessing, and after he finishes the blessing he separates it, so that the blessing ends while the loaf is whole. He should not break a small piece, because it looks stingy, nor a piece more than an egg, because it looks like a glutton. The Rema adds: on Shabbat he should not cut the loaf until after the blessing, so that the loaves remain whole; but in any case, if he forgot and cut as on a weekday, it does no harm. And it seems that the rule of not more than an egg applies only on a weekday, eating alone; but on Shabbat, or when eating with many people and he must give each one a kezayit from the piece, it is permitted to break as much as he needs; and see siman 274.

He recites the blessing: "HaMotzi lechem min ha'aretz." The Rema adds: if many people are reclining together, they should focus their hearts to hear the blessing and answer Amen. The one saying the blessing should have in mind the Amen that they say. He should leave a space between "lechem" and "min."

One may not recite the blessing over bread before he has taken hold of the bread.

A person puts both hands on the bread at the time of the blessing, because the hands have ten fingers, corresponding to the ten mitzvot that depend on bread. Therefore there are ten words in the blessing of Hamotzi, ten words in the verse "Matzmiach chatzir labehemah", ten words in the verse "Einei kol eilecha yesaberu", ten words in the verse "Eretz chitah useorah", and ten words in the verse "Veyiten lecha".

One should not break bread until salt or a liftan (Rashi explains: anything that is eaten with bread) is brought before him, to dip the piece of the broken bread in. But if the bread is clean, or it is spiced with spices or with salt like ours, or he meant to eat plain dry bread, he does not need to wait. The Rema adds: even so, it is a mitzvah to place salt on every table before breaking bread, because the table resembles the altar and the eating resembles a sacrifice, and it is said, 'on all your sacrifices you shall offer salt' (Beit Yosef in the name of Shibbolei HaLeket). And it protects from calamities (Tosafot and Hagahot Asheri, perek Keitzad Mevarchin); and see above at the end of siman 170.

He should eat right away, and not speak between the blessing and the eating. If he did speak, he must go back and bless again — unless the speech was about matters connected to the food he blesses over. For example: he blessed over the bread, and before he ate he said, "Bring salt or relish," or "Give so-and-so something to eat," or "Give food to the animal," or the like — he does not need to bless again. The Rema adds: nevertheless, ideally one should not interrupt at all. And the rule that if he spoke idle words he must bless again applies specifically when he spoke before the one who breaks bread ate. But afterwards it is not an interruption, even though the other people at the table have not yet eaten: they have all fulfilled their obligation with the eating of the one who broke bread, because they do not all need to eat from the piece of the one who broke bread; they only do so to endear the mitzvah.

Reuven was washing his hands in order to eat. Yaakov was saying the blessing Hamotzi, and he intended to exempt those listening. Afterwards Reuven dried his hands and said the blessing al netilat yadayim (over washing the hands). This is not considered an interruption, and Reuven fulfills his obligation with Yaakov's blessing. He does not need to go back and say the blessing Hamotzi again.

A person forgot and ate without reciting the blessing over bread. If he remembers during the meal, he recites the blessing then. But if he does not remember until he has finished his meal, he does not recite it.

If he is in doubt whether he blessed HaMotzi or not, he does not go back and bless.

If a person blessed 'Shehakol nihya bidvaro' in place of the Hamotzi blessing, he has fulfilled his obligation. The same applies if he said 'Brich rachmana malka marei dehai pita' — 'Blessed is the Merciful One, King, Master of this bread'.

If two or more people are eating, one of them says the blessing for all. This applies specifically when they reclined, which is the manner of a fixed meal. The Rema adds: or a homeowner with the members of his household, which counts like reclining (Tur). But if they were sitting without reclining, since they are not made fixed together, each one blesses for himself. And if they said, "We will eat here" or "in such-and-such a place," since they prepared a place for their meal, it counts as fixed, even without reclining. And nowadays, when we are not accustomed to reclining, our sitting at one table, or without a table on one cloth, counts as fixity; and even for the members of a group it is considered like their reclining. But for us, even if they fixed a place for their meal, or a homeowner with his household, it helps only if they sat at one table or one cloth.

If they were riding and said, 'We will eat,' even though each one eats from his own loaf, since they did not get down from the animals, they join together, since they stood in one place. But if they were eating while walking, no. And if they were eating in a field scattered and separated, even though they all eat at the same time and from one loaf, since they did not fix a place and are eating scattered, they do not join.

When a group has not fixed a place, the rule is that each person makes the blessing for himself. Even so, if the one making the blessing intended to fulfill the obligation for the others, and they intended to fulfill it through him, they have fulfilled their obligation.

If the ones reclining are many, the greatest of them all breaks bread. The Rema adds: if they are equal and one of them is a kohen, it is a mitzvah to give him precedence; but if the kohen is an am ha'aretz (an unlearned person), a talmid chacham comes before him; and if the kohen is also a talmid chacham, only that he is lesser than the second, it is good to give him precedence, but there is no obligation in the matter. See above, siman 201 (and the Mordechai, chapter Bnei Ha'ir, Beit Yosef siman 135, in the name of the Rashba). And if there is with them a ba'al habayit (a host), he breaks bread, even if the guest is greater. The Rema adds: and the one who blesses should say first 'birshut morai verabbotai' (Or Zarua, and Beit Yosef in the name of Shibbolei HaLeket).

The people reclining at the meal are not allowed to taste until the botzeia (the one who breaks bread) tastes. The Rema adds: but it is permitted to give each one his portion before he eats, and they wait until he eats. And if each one eats from his own loaf, and they are not all dependent on the loaf in the botzeia's hand, they are permitted to taste first. And if it is Shabbat, there must be a second loaf before the reclining ones, besides what is before the botzeia, and then they are permitted to taste before the botzeia.

The one who breaks bread is not allowed to break until the Amen has finished coming from the mouth of most of those who answer.

The one who breaks bread stretches out his hand to the dish first, to eat. And if he comes to give honor to someone who is greater than he is, he is permitted.

The one who breaks bread gives a piece before each person, and each person takes a piece in his own hand. The one who breaks bread does not put it into the hand of the eater, unless the eater was a mourner. The Rema adds: 'Zion spread out her hands' (Eichah 1:17) is a hint to the piece of hamotzi that they give into his hand during mourning, citing Beit Yosef and Avudraham in the name of Rambam, p'z of Hilchot Berachot, and the responsa of Rashba.

A person who is not eating cannot recite the blessing of Hamotzi in order to exempt the people who are eating. But for children he may recite it even though he is not eating together with them, in order to train them in mitzvot.

Even on Shabbat, when a person is obligated to eat bread, his friend may not recite the motzi blessing for him if he is not eating. And it is not permitted to bless for others even though he does not taste, except for the motzi blessing of matzah on the first night of Pesach, and the wine blessing of kiddush, whether of the night or of the day. The Rema adds: one should eat the piece he broke the blessing on before eating other bread, so that it is eaten with appetite; this is because of cherishing the mitzvah.