The Shabbat candles should be lit before sunset, but no more than 1¼ hours1 before sunset (also known as plag haminchah).2 It's never wise to procrastinate until the last moment, so it is customary to light the candles no later than eighteen minutes before sunset.3 (Others have the custom to light twenty-three minutes prior to sunset.4) To find out the candle-lighting time (i.e., eighteen minutes before sunset) or plag haminchah for any date and for any location in the world—click here.

Women should pray the afternoon prayers prior to lighting the candles. If one is pressed for time, the candles should be lit with the intention of not accepting Shabbat until after the prayers—which should be recited immediately after the lighting.5

It is customary to light the candles while clad in Shabbat finery.6

With the lighting of the candles, the kindler is effectively ushering in the Shabbat. As soon as all the candles are lit, even before the blessing is recited, all forms of work are prohibited.7

If a woman makes a condition, even if she has not verbally expressed the condition, that she is not accepting the Shabbat with the lighting of the candles, she is permitted to continue working until approximately ten minutes after she lit the candles. This is especially useful when one is lighting candles at home and then needs to drive to the synagogue. This condition should only be used in times of need; ideally, Shabbat should be accepted immediately with the lighting of the Shabbat candles (otherwise it isn't readily evident that the candles are lit solely in honor of Shabbat).8

If one has, G‑d forbid, forgotten to kindle the Shabbat candles before sunset, within the first fifteen minutes a non-Jew should be requested to light one candle. The Jew then covers her (or his) eyes and recites the blessing with a slight variation:

Baruch a-ta A-doi-nay Elo-hei-nu me-lech ha-o-lam a-sher ki-dee-sha-nu bi-mitz-vo-tav vi-tzi-va-noo al had-la-kat ha-ner.9

("Blessed are you, L‑rd our G‑d, King of the universe, who has sanctified us with His commandments, and commanded us regarding the kindling of the candle.")

This only applies for the first fifteen minutes after sunset. After that time has elapsed, one is not allowed to ask a non-Jew to light a candle.10