The Chanukah lights should be lit when the stars appear. If one did not light then, one may still light through the remainder of the night, provided that the members of the household are still awake. If one was inadvertently unable to light the Chanukah lights until very late – when everyone is already asleep (and it is not possible to awaken two or three of them) and thus one cannot achieve publicizing of the miracle – he should light without making a blessing. Once night has passed, the lights cannot be lit and one cannot make up for having failed to perform the mitzvah. He can only light the next evening as does everyone else.
For the half hour preceding the time when the lights are to be lit, one is forbidden to eat a "fixed" meal or to partake of anything intoxicating. When the prescribed time has arrived, even the study of Torah is prohibited until the Chanukah lights are lit. When the stars appear, the evening prayers are recited and is followed immediately by the lighting of the Chanukah lights. In Jerusalem, many follow the custom of the Vilna Gaon and light the Chanukah lights at sunset, prior to the evening prayers.
The lights should burn for at least half an hour; thus, when lighting, there should be sufficient oil for them to burn for that amount of time. Those who light at sunset must place sufficient oil for the lights to burn for at least fifty minutes – twenty minutes from sunset until the appearance of the stars and thirty minutes afterwards.
If, at the time when the lights were lit, there was an insufficient amount of oil for them to burn for the requisite period, one has not fulfilled the mitzvah and one may not add oil after the lights have been lit. Rather, one must extinguish the flame, add oil, and relight the lights without the blessing. The essence of the mitzvah is the act of lighting – thus, there must be sufficient oil at the time of lighting to burn for the required time.
If one poured more than the required amount of oil for the lights, he may extinguish them after they have burned for more than half an hour after the appearance of the stars, if he wishes to use the excess oil for lighting on the following evening. He may also extinguish the lights in order to use the remaining oil for some other purpose, provided that he specifically stipulated that he had intention to do so before he used the oil for the Chanukah lights. For this reason, no use may be made of the oil or wicks that remain after the last night of Chanukah unless one specifically stipulated – before lighting – that he intended to use whatever remained for other purposes. If he made no stipulation, they should be burned.
If the Chanukah lights were accidentally extinguished during the prescribed period, they should be relit without a blessing. If one failed to relight them, he will nevertheless still have fulfilled the mitzvah, for as we have seen, the essence of the mitzvah is the act of lighting.
As long as the Chanukah lights are burning – even if the prescribed period has passed – no benefit may be derived from their light and they may not be moved from place to place. If one wants to use their light for some other purpose after they have burned for the prescribed period, he should first extinguish them and then relight them [only if he made a stipulation – as above].
On Friday afternoon, the lighting of the Chanukah lights precedes the lighting of the Shabbat candles. One should be careful to use sufficient oil to ensure that they remain lit for at least half an hour after the appearance of the stars.
On motza'ei Shabbat (Saturday night), customs differ – among many, the Chanukah lights are lit after Havdalah; others reverse the order. A person should therefore follow the custom of his forefathers. Among Sephardic communities, Chanukah lights are lit in the synagogue before Havdalah and at home, Havdalah precedes the lighting.