At first, Mizrahi Jews would add dirges (kinnot) for the destruction only on the three sabbaths that are between the Seventeenth of Tamuz and Tisha B'Av, and not on weekdays. After discussions that questioned this practice of mourning specifically on the Sabbath, it was decided to discontinue the recitation of the kinnot on these days. Rabbi Isaac Luria cancelled the customs of mourning on the Sabbath but declared that the Tikkun Chatzot should be said each and every day.
The Poskim mention a custom to recite Tikkun Chatzot during the day time during these weeks between the Seventeenth of Tamuz and Tisha B'Av. This custom is observed in some communities.
The Tanya mentions that one should recite Tikkun Chatzos every night if one can. He then suggests that if one cannot do so every night, they should do so on Thursday Nights, as a preparation for the Sabbath.
Tikkun Chatzos is divided into two parts; Tikkun Rachel and Tikkun Leah, named for the two wives of the Patriarch Jacob. On days when Tachanun is not recited during daytime prayers, only Tikkun Leah may be recited (although many do not recite Tikkun Chatzos at all on such days).
According to Siddur Beis Yaakov, by Rabbi Yaakov Emden, Psalm 102, the "Prayer of the afflicted," is read before reciting Tikkun Rachel. Afterwards, one begins the actual service by reciting the Viddui confession including Ashamnu, and then one reads Psalm 137, "By the rivers of Babylon," and Psalm 79, "A song of Asaph." Afterwards, verses from the book of Lamentations are read, followed by the kinnot, with customs varying among the communities, the general custom being to recite five or six kinnos specifically composed for Tikkun Chatzos, some of which were composed by Rabbi Moshe Alshich. The Tikkun Rachel service is concluded with the reading of Isaiah 52:2, "Shake thyself from the dust..."
Tikkun Leah consists of various Psalms, and is recited after Tikkun Rachel, or alone on days when tachanun is omitted. The Psalms of Tikkun Leah are Psalm 24, 42, 43, 20, 24, 67, 111, 51, and 126. Psalms 20 and 51 are omitted when Tikkun Rachel is not said. Other Bible verses and short prayers are then said, followed by study of Mishnah, the last chapter of tractate Tamid. Many study Zohar after this.