479. One is obligated to fast on the Public fast days established by The Nevi-im which are: Tisha B'Av (9th of Av), 17th of Tammuz, 3rd of Tishrei (Tzom Gedalaya), 10th of Teves, and the 13th of Adar (Taanis Esther). (In the coming days we will discuss the obligation with respect to women). Shulchan Aruch w/Mishnah Brurah 549:1
 
480. On all these days we fast because of the tragedies that happened; to remind us that our behavior today is similar to the behavior of our forefathers which caused the tragedies, and to awaken us to do Teshuvah. Shulchan Aruch w/Mishnah Brurah 549:1
 
481. On all the Public fast days one is obligated to focus one's attention (mind and heart) to examine one's behavior and to do Teshuvah.
Shulchan Aruch w/Mishnah Brurah 549:1
 
482. The focus on Teshuva is even more important than the fasting itself; Therefore, those who fast, but spend the day on trips or tours have "grabbed onto the (thing of) minor (importance) and left over the (thing of) major (importance)".
Shulchan Aruch w/Mishnah Brurah 549:1
 
483. Five tragedies happened on the 17th of Tammuz;
 
1. The 1st Luchos were broken;
2. The Korbon Tamid was unable to be brought any longer (1st Beis Hamikdash);
3. Yerushalayim was breached (2nd Beis Hamikdash); (and 1st Beis Hamikdash according to
    Gemara Yerushalmi. Other opinions say that it occurred on the 9th of Tammuz);
4. Apostomus Ha'Rasha burned the Torah;
5. and placed an idol in the Heichal of the Beis Hamikdash;
Shulchan Aruch w/Mishnah Brurah 549:1
 
484. Five tragedies happened on Tisha B'Av;
 
1. The 1st Beis Hamikdash was destroyed;
2. The 2nd Beis Hamikdash was destroyed;
3. It was decreed that all the Jews in the Midbar would not enter Eretz Yisroel;
4. The city of Beitar was captured and thousands of Jews were murdered;
5. Turnisrufus Ha'Rasha plowed the Heichal and the Mokom Hamikdash
Shulchan Aruch w/Mishnah Brurah 549:1
 
485. If one forgot that it was a fast day and unintentionally ate; one should nevertheless complete the rest of the fast day without eating.
Shulchan Aruch w/Mishnah Brurah 549:1
 
486. On a fast day one should be particularly careful to avoid anger. If one is conducting business, one should be extra diligent to behave in a calm and peaceful manner to avoid anger.
Shulchan Aruch w/Mishnah Brurah 568:12
 
487. There is a minhag (mentioned in Tosafos Mes. Megillah beg. Chapt. 3) to give Tzedakah at Mincha on the day of a Taanis. The mitzvah of Tzedakah is mentioned in the Haftorah that is read at Mincha on a Taanis. Shulchan Aruch w/Mishnah Brurah 566:2 MB12
 
488. Some also have the minhag to estimate the value of the food cost being saved due to the fast, and give that amount to the poor to eat for the evening meal.
Shulchan Aruch w/Mishnah Brurah 566:2 MB12
 
489. On the day of a Taanis one should refrain from unnecessarily touching foods, lest one inadvertently eat during the fast.
Piskei Tshuvos 589:1 citing Pri Migadim 612 citing Taz 612:8
 
490. Restaurant owners should be aware that serving food on a Taanis to someone who is obligated to fast (as opposed to a sick person for example - who may eat) may involve the issur of Lifnei Iver - "Placing a stumbling block before a blind man". Therefore, the decision of whether to remain open on a Taanis should be discussed with a Rov.
S"U Maharsham 6:11, S"U Bais Shlomo 38, Yalkut Yosef - Moadim 530
 
491. Generally, The obligation to fast on public fast days includes women.
                       
A) Nevertheless, many contemporary Poskim are lenient with regard to (married) women who are of age to bear children, and allow them not to fast on the four fasts (excluding Tisha B'Av & Yom Kippur).
 
B) However, inasmuch as this leniency is not in accordance with Shulchan Aruch and many other Poskim, one should not be lenient without the specific direction of a Rov/Posek.
Shulchan Aruch w/Mishnah Brurah 550:1, Piskei Tshuvos 550:1
 
492. Women who are nursing or pregnant (according to Mishnah Brurah - more than 40 days into the pregnancy), are not obligated to fast on the four fasts (excluding Tisha B'Av & Yom Kippur), and those who fast are acting according to the minhag to be strict.
Shulchan Aruch w/Mishnah Brurah 550:1
 
493. A pregnant or nursing woman who is feeling weak (and certainly one who is sick) may not fast. Shulchan Aruch w/Mishnah Brurah 550:1
 
494. Anyone who is feeling sick is not obligated to fast, and may not act strictly in this regard. (The same is true for people who are weak or old and have been advised by a doctor that fasting could harm their health.)
Shulchan Aruch w/Mishnah Brurah 550:1, Piskei Tshuvos 550:2
 
495. One who is eating on a fast day (due to sickness, pregnancy or other permission) should not indulge oneself (with meat or wine). Rather one should only eat what he needs to sustain himself.
Shulchan Aruch w/Mishnah Brurah 550:1
 
496. During the three weeks beginnining with the 17th of Tammuz until after Tisha B'Av we behave with minhagim of mourning for the destruction of the Beis Hamikdash, getting progressively stricter on Rosh Chodesh Av (beginning the 9 days) and the week within which Tisha B'Av falls. Shulchan Aruch w/Mishnah Brurah 551
 
497. Beginning with the 17th of Tammuz and for the entire 3 week period we do not make weddings, listen to music, dance, take haircuts/shave, wear new clothing or eat a new fruit  which would require a Beracha of Shehechiyanu (except on Shabbos) or hit children.
Shulchan Aruch w/Mishnah Brurah 551:1,2,12,14,17,18
 
498. If one has a court matter pending with a non-jew during the 3 weeks, he should preferably adjourn the case until the Month of Elul, but at least until after Tisha B'Av.
Shulchan Aruch w/Mishnah Brurah 551:1
 
499. During the 3 weeks one should refrain from going to any dangerous place, (ie. swimming in an ocean or river) and certainly one should be extra careful during the 9 days from Rosh Chodesh Av until after Tisha B'Av, (because one's mazel is weak during this period).
Piskei Tshuvos 551:1,46
 
500. From the 17th of Tammuz until Rosh Chodesh Av one is permitted to swim, even for one who has not gone swimming yet this Summer.
Tshuvos V'Hanhagos 2:263, Piskei Tshuvos 551:46
 
501. During the 3 weeks one is permitted to conduct regular business dealings.
Shulchan Aruch w/Mishnah Brurah 551:2, see also Sha'ar Hatziyun 13
 
502. If one has started construction of an extension or re-painting of his home, before the 3 weeks, one may have the work continue until Rosh Chodesh Av, at which point one should try to push the contractor off until after Tisha B'Av. However, one may not begin work after the 17th of Tammuz. Shulchan Aruch w/Mishnah Brurah 551:2,
 
503. Nevertheless, one may hire a contractor during the three weeks to make any necessary repairs to his home. Piskei Tshuvos 551:8
 
504. One should not schedule surgery during the 3 weeks, and certainly not during the 9 days, unless the doctor insists that it cannot medically be postponed. Piskei Tshuvos 551:1
 
505. During the 3 weeks one is permitted to make preparations for a wedding scheduled for after Tisha B'Av including the sewing and purchase of new clothing and other items needed for the wedding. Shulchan Aruch w/Mishnah Brurah 551:2
 
506. During the Nine days (beginning Rosh Chodesh Av) the custom is that one does not wear freshly laundered clothing. Therefore, one should wear all the clothing one will need during the Nine days for one hour, sometime before the start of the Nine days. One may wear multiple layers of clothing to accomplish this. Some poskim permit one to lay the clothing on the floor, which also removes its freshly laundered status and permits one to wear it during the Nine days.
Shulchan Aruch w/Mishnah Brurah 551:3, Piskei Tshuvos 551:17
 
507. During the Nine days the custom is that one does not do any laundry, even via a non-jewish housekeeper. However, one may bring laundry to a non-jewish cleaners before the Nine days even if one knows that that they will launder the clothing during the Nine days.
Shulchan Aruch w/Mishnah Brurah 551:3
 
508. During the Nine days (beginning Rosh Chodesh Av) one may not make a major purchase (e.g. a new car, furniture - normally used by the entire family) because this would require one to make a beracha of Hatov V'Hameitiv which one cannot make during the Nine days.
Shulchan Aruch w/Mishnah Brurah 223:5, 551:2 MB11, see Sha'ar Hatziyun 13, Igros Moshe 3:80, Nitay Gavriel pg. 51
 
509. During the Nine days one may not purchase any clothing or shoes (or even inexpensive items such as socks) even if one does not intend to wear it until after Tisha B'Av. (Prior to Rosh Chodesh Av one may purchase inexpensive clothing items which would not require a Shehechiyanu). Shulchan Aruch w/Mishnah Brurah 551:7
 
510. During the Nine Days it is permitted to purchase items which a) do not require a beracha of Shehechiyanu or Hatov V'Hamaitiv, and b) are not clothing.
Shulchan Aruch w/Mishnah Brurah 551
 
511. During the Nine days, even when purchasing is prohibited, only actual buying is prohibited. Comparison shopping and window shopping is permitted.
Shulchan Aruch w/Mishnah Brurah 551
 
512. If one needs non-leather shoes for Tisha B'Av one may purchase them during the Nine days. Igros Moshe 3:80
 
513. If one will run out of clothing for small children to wear in the Nine days one may purchase them during the Nine days. Mishnas Yaakov 551 citing Magen Avraham
 
514. If there is a big sale and one will be unable to purchase the same clothing after Tisha B'Av at the sale price, one may make the purchase during the Nine days, but may not wear the clothing until after Tisha B'Av. S'U Kinyan Torah 1:109 cited in Piskei Tshuvos 551:27
 
515. During the Nine day, although one may not do laundry, or bring laundry to a non-jewish cleaners, it is permitted to do laundry for small children in small loads if necessary.
Shulchan Aruch w/Mishnah Brurah 551:3, 14
 
Halacha L'kovod Shabbos -  "Halachos pertaining to Erev Tisha B'Av on Shabbos"
1. Although one normally should not study Torah on erev Tisha B'Av after Chatzos (except for Torah portions permitted on Tisha B'Av itself) when erev Tisha B'Av falls on Shabbos one should fulfill his regular Shabbos Torah study, however, it is customary not to learn Pirkei Avos after Chatzos. Shulchan Aruch w/Mishnah Brurah 553:2
 
2. The usual Seudah Mafsekes is replaced with a regular Seudah Shlishis of Shabbos at which one may eat meat and drink wine and eat any foods one desires. One may eat the meal with the  family at one table, however, one should not invite guests unless one regularly has guests  for Seudah Shlishis. One may conclude the meal with a Zimun as always. One must be careful to conclude the meal before sunset/Sh'kiah - NYC time 8:02 pm. One should not say that he is eating to have strength for the fast, and one may not take a pill that makes it easier to fast, because one would be preparing on Shabbos for Sunday which is not permitted. One may sing zemiros. Shulchan Aruch w/Mishnah Brurah 552:10, Shmiras Shabbos Kehilchasa 28:77, Igros Moshe 4:112
 
3. If one completed the 3rd seudah before sunset and said Birchas Hamazon one may eat and drink until sunset without making any t'nai (condition).
Sha'ar Hatziyun 553:7
 
4. One may sit on a chair until nightfall NYC time 8:47 pm.
Shmiras Shabbos Kehilchasa 62:88
 
5. No preparations for Tisha B'Av may be made on Shabbos. One may not bring Tisha B'Av shoes or Kinos to shul on Shabbos even if there is an eruv. Therefore, it is advisable that one should bring these items to shul before Shabbos.
Shmiras Shabbos Kehilchasa 28:77
 
516. There is a machlokes H'Poskim whether one may cut their nails during the Nine days. The Taz prohibits it, while the Magen Avraham permits it. Therefore L'kovod Shabbos one may cut their nails on Friday. Shulchan Aruch w/Mishnah Brurah 551:3
 
517. According to some Poskim only one who cuts their nails every Friday L'kovod Shabbos may cut their nails on the Friday before Tisha B'Av.
Eliyahu Rabbah 551, Yad Efraim 551, Kaf Hachaim 551:48, Piskei Tshuvos 551:19
 
518. A Shaitel is categorized as an article of clothing for purposes of the halachos of the Nine days. Therefore one should not wash a shaitel or have it professionally cleaned and/or set during the Nine days. Piskei Tshuvos 551:20
 
519. However one may curl or set a shaitel at home during the Nine days (presuming that one is not a professional "shaitel macher"). Piskei Tshuvos 551:20
 
520. The minhag is that one should not say Kiddush Levanah until after Tisha B'Av. Many have the minhag to follow the opinion of the Ari'zal who says that because Motzai Tisha B'Av is the Birthday of Ben-Dovid ie. Moshiach one should preferably say it that night.
Shulchan Aruch w/Mishnah Brurah 551:8, see Be'er Haitaiv 25, Levushei Srad 551:8,
 
521. Before saying Kiddush Levana on Motzai Tisha B'Av one should wash his hands, eat something, and put on regular shoes.
Shulchan Aruch w/Mishnah Brurah 426:MB11, see Sha'ar Hatziyun
 
522. Although one may not eat meat or drink wine during the Nine days, stores that sell meat and wine may remain open during the Nine days because they may be needed to service those who are permitted to eat meat (or drink wine) such as one who is sick, or making a seudas mitzvah (bris, pidyon haben, siyum mesechtah). IgrosMoshe 4:112
 
523. Furthermore, one is permitted to purchase meat and wine during the Nine days for use after the Nine days if there is a sale, or one will not have time afterwards. Igros Moshe 4:112
 
524. One is permitted to shine their shoes L'Kovod Shabbos.
Igros Moshe 3:80
 
525. The custom is that the restrictions of the Nine days (including bathing, cutting hair, doing laundry, listening to music, making a beracha of Shehechiyanu, eating meat, drinking wine) continue until Chatzos on the Tenth of Av (NYC 1:01pm).
Shulchan Aruch w/Mishnah Brurah 558:1
 
Halachos of Tisha B'Av that begins Motzai Shabbos