The bare minimum requirement of light for oneg Shabbos is one simple candle. If you have the means, beautify that one before adding a second one. There is an inyan to light one for “Zachor” and another for “Shamor”. There are various minhagim to light even more than two. (ShA1 – MB1,3,6,22)
The reward for beautifying this mitzva is talmiday chochomim for sons. Therefore it is fitting to pray for this after the beracha. (MB2)
Although the beracha should be recited on the ner which is lit in the dining area, you should have light in every room so you don’t stumble in the dark on Shabbos. (MB2)
When lighting more than one ner, do not take a flame from the first one to transfer it to the second one by means of a non-mitzva wick. Direct lighting from one mitzva to another is allowed. (MB4)
A woman who forgets to light nairos one Shabbos is liable for a penalty: add another ner each time for the rest of her life. This is to remind her to be more cognizant of her obligation. If it was a situation beyond her control there is no penalty. (Rama1 – MB7)
Men and women are obligated to have light in their homes on Friday night. But since women are more involved in the needs of the house, they are more warned about this mitzva and therefore have a right to it before the husband. He can light if there are many lamps to light. The first Shabbos after a woman gives birth the husband lights and says the beracha. (ShA2,3 – MB11)
The husband should set up the candles for his wife. (MB12)
If you do not have enough money to afford all of the mitzvos, here is a list of priority in descending order of importance:
Bread for the seuda. (You can say kiddush on the bread.)
One single ner for Shabbos.
One single Chanukah ner.
Wine for Kiddush.
More Channuka nairos.
More food for Shabbos. (ShA3 – MB9,14
Lamps that are lit on Friday afternoon (even after Plag Hamincha) not for the purpose of Shabbos cannot count for ner Shabbos. They must be extinguished and relit for Shabbos. (Rama4 – MB20)
The nussach of the beracha is “asher kid’shanu b’mitzvosov v’tzivonu l’hadlik ner shel Shabbos.” On Yom Tov, replace the ending with “…ner shel Yom Tov”. If Yom Tov occurs on Shabbos the nussach becomes “..ner shel Shabbos v’shel Yom Tov.” (ShA5 – MB24)
You do not need to say Shehecheyonu together with the beracha on the Yom Tov lamps. Do not protest in places that do. (MB23)
The minhag of women is to light the Shabbos lamps before the beracha. Block the candlelight with your hands so as not to benefit from it before the beracha. Then, remove your hands after the beracha – you have fulfilled reciting the beracha before the mitzva. The Mogen Avraham says to do the same on Yom Tov, however many achronim hold to light Yom Tov candles only after the beracha. (Rama5 – MB27)
When your wife lights in the dining area, you still need to light up the other rooms for shalom bayis. However, the beracha on one room covers all the others – similar to bedikas chometz. (BeH “bachurim”)
A man who is away from home must have light for shalom bayis in the room he is staying in. This requires a ner Shabbos with a beracha even if he will not be eating there. The candles must be long lasting so he will not be in the dark when he returns to the room, otherwise it will be a beracha l’vattala. (ShA6,9 MB29,30)
Many men together in one room must pitch in to buy ner Shabbos for shalom bayis. Their wives’ lighting at home does not exempt them. One person should light and say the beracha having the rest in mind. The others also should have kavana to be yotzay the beracha. (MB30)
If you are a guest and the host will be providing light in your room – shalom bayis is taken care of. All that is left is the personal obligation for every Jew to light ner Shabbos. So, if your wife is lighting at home, that covers you – if you are single you must be a partner with your host by giving a coin for the ner Shabbos. (ShA7 – MB30 – BeH “bachurim")
When many families are eating in one place there is a dispute if the nairos lit after the first one require a beracha. Our minhag to say a beracha since all additional nairos add more shalom bayis and simcha. A family that has a private room can light there with a beracha for sure, even though no dining is done there. (ShA8 – MB35,38)
The Friday night meal must be enjoyed by the candle light unless there are disturbing flies (and the like) there. Technically the candles used for the meal or to prepare food for the meal do not need to last until dark. Still, the best way is for the candles to last into the night even though you want to eat while it is still daylight. (MB39,40,41)
The minhag is that a woman accepts Shabbos with the lighting of Shabbos nairos. Therefore she should daven Mincha beforehand. If time is short she should first light and then daaven Maariv twice. She can make a condition not to accept Shabbos until sometime after she lights, if necessary. There is no need to verbalize the condition. (Rama 10 – MB43,44)
Two examples of a necessity to make a condition are:
To attend a chuppa Friday late afternoon. She can light with a beracha first with the intention not to accept Shabbos until later.
Toiveling in the mikva Friday night. She should light with a beracha with the intention not to accept Shabbos until after bathing and shampooing. The Chayay Odom says to say the beracha before lighting in cases when she isn’t accepting Shabbos yet. (MB21 – BeH “achar”)
Do not move the nairos once they are lit for Shabbos even if you haven’t accepted Shabbos yet. If necessary, you can rely on an opinion that holds you may move them in the house from one place that you will need light to another place that you will need light. (Rama 10 – MB47,48)
If you proceed to daaven Maariv before the kahal while it is still light you have automatically accepted Shabbos. (ShA11)
In a town with one shul and most people accepted Shabbos in the shul, everyone in the town automatically accepts Shabbos with them (in regards to melacha but not in regard to davening. The individual may still daaven Mincha). If there are many shuls, even the majority cannot bind all of the other shuls. (ShA12 – MB51 – BeH “shel”)
If you come late to the “early Shabbos” minyan you may begin Mincha (it is best to exit the shul) as long as they have not yet said Borchu for Maariv. Once you answer Borchu, it’s too late –daaven Maariv twice. (ShA15,16)
Unlike on Friday, once Shabbos is over you may break away to say Havdalla and do melacha even though the tzibbur is still keeping Shabbos. (MB67)
Even if you are still keeping Shabbos, you are allowed to instruct Jews who have already said Havdalla to do melacha for you and benefit from it. (Rama17)
If you said “hamavdil bain kodesh l’chol” before benching for Shalosh Seudos, you may do melacha but there is a doubt if you can say R’tzay in benching or not. (MB67)