One should strive to pray about the destruction of the Bet HaMikdash and the exile at each third of the night since that is the time that tefillot are most acceptable.
Siman 1 Seif 3:
It is appropriate for those who have Yirat Shamayim to be troubled by the destruction of the Bet HaMikdash.
❖ Tikun Chatzot consists of chapters from Tanach that are recited to mourn the destruction of the Bet HaMikdash. The order can be found in the siddurim. (M.B. 9)
❖ During the recitation of Tikun Chatzot a person should sit on a mat on the floor by an opened entrance without shoes and he should put burnt ashes on his head where he puts his tefillin. (Ben Ish Hai Vayeshev 11)
❖ It should be recited at midnight which is 12 hours after mid-day.(M.B. 9) It cannot be recited before midnight and not after Alot Hashachar (dawn) (Ben Ish Hai Vayishlach 4, 8)
❖ People that reside outside of Israel can be lenient to recite Tikun Chatzot if midnight of Israel has past even though midnight of where they reside has not past (Halacha Berurah 1:5)
❖ It should not be recited on Shabbat and Holidays. (Ben Ish Hai Vayishlach 7)
❖ Tikun Chatzot takes precedence over learning Torah and reciting Selichot. (Ben Ish Hai Vayishlach 9)
❖ Tikun Chatzot takes precedence over praying at netz (sunrise). (Or Lesion 1:12) Other poskim disagree and hold praying at netz takes precedence. (Ish Matzliach 1:6)
❖ It is better to sleep and be well rested than to rise early and be left without strength. (M.B. 9)
❖ One should rise an hour or at least half an hour before praying so that he will have time to prepare his body for praying. (M.B. 9)
❖ The Shelah writes that one should read chapter 137 (על נהרות בבל)ל of Tehillim at all meals and on days that Tachanun is not recited one should read chapter 126 (שיר המעלות) and it is important to understand what one is reciting. (M.B. 9)
HALACHA HIGHLIGHTS
AT WHAT AGE DO CHILDREN BEGIN TO WASH THEIR HANDS IN THE MORNING ?
Mishnah Berurah 9
והמקובלים האריכו מאד בגודל מעלת קימת חצות
The Kabbalists elaborated on the great advantage of waking up at chatzot
Mishnah Berurah (א:ט) relates that the mekubalim elaborate on the importance of saying Tikun Chatzot. His language implies that although it is an important tefilla to recite it is not an absolute obligation. Sefer Mor U’Ketzia (ס׳ א ד״ה ולכן) also writes that he did not find even a hint in the Gemara that one should arise to pray at chatzot. When the Zohar discusses the recitation of Tikun Chatzot the intent was not to establish a binding obligation on everyone. Only talmidei chachamim living in Eretz Yisrael are obligated to recite this tefilla.
The Chida (מחזיק ברכה (סימן א אות א disagrees with Mor U’Ketzia and maintains that it is an obligatory tefilla, and in his work Shem Hagedolim he explains why it is not mentioned in the Gemara.
Rav Chaim Kanievsky (בספר עוז מאיר סימן א) maintains that the practice of reciting Tikun Chatzot is the same as all Kabbalisticly based practices that do not generate an obligation for all to observe.
A number of explanations are given why it is not so common for people to recite Tikun Chatzot nowadays. Eshel Avraham suggests that we are no longer as strong as earlier generations and physically we could not handle waking each night to recite Tikun Chatzot. Another explanation (פסקי תשובות) is that due to the duration of the exile and all of the burdens that weigh on our minds regarding our immediate needs it is difficult for people to generate the sadness that is supposed to accompany the recitation of Tikun Chatzot.
Mishnah Berurah (א:ט) also writes that those who know that if they were to rise for Tikun Chatzot would not be able to wake up to pray shahrit do not have to rise for the recitation of Tikun Chatzot. On the other hand, the Ben Ish Hai (רב פעלים ח״א סימן א) writes that even if a person is preoccupied and it is hard to have the right thoughts, he should still read Tikun Chatzot and try to have as much kavanah as he can. The Petach HaDevir (11) says that if a person is very busy with his business dealings, he should support a Ben Torah that will recite Tikun Chatzot and through that he will also get reward.