1358. From Rosh Chodesh Sivan until the 8th of Sivan (Isru Chag) we do not say Tachnun.
Shulchan Aruch w/Mishnah Brurah 494:3, Piskei Tshuvos 494:9
1359. Some do not say Tachnun until the 12th of Sivan, and in the Diaspora until the 13th of Sivan.
Shulchan Aruch w/Mishnah Brurah 494:3, Piskei Tshuvos 494:9
1360. On Shavuos at night the minhag is to wait until it is night (Tzeis Hakochavim) to daven Maariv in order to have 49 complete days. Shulchan Aruch w/Mishnah Brurah 494:1
1361. Likewise, it is preferable for women to wait until it is night to light candles and say Shehechiyanu on Shavuos night. Luach R' Yechiel Michel Tukatchinsky, Piskei Tshuvos 494:2
1362. There is a minhag (brought in The Zohar) to stay up the night of Shavuos and learn Torah. This is based on the Midrash which says that Klal Yisroel overslept the night before Matan Torah and Hashem had to awaken them to receive the Torah. Therefore we stay up all night to rectify their oversight. Shulchan Aruch with Mishnah Brurah 494:1
1363. The Ari'zal writes that one who does not sleep the night of Shavuos and toils in Torah is assured to live out the year and no harm will occur to him. Shulchan Aruch with Mishnah Brurah 494:1
1364. There is a compilation of torah learning known as "Tikkun Lay'l Shavuos" which has The Zohar and the writings of The Ari'zal as its source, and many have the minhag to say/learn this on Shavuos night. Kaf Hachaim 106:7, Lev Dovid L'Hachidah.
1365. Generally women should not say the "Tikkun Lay'l Shavuos". However, some say that a woman who counted all the days of Sefiras Ha'omer may learn the portions of the Tikkun which are from Tanach. S'U Rav Poalim 1SY:9, Kaf Hachaim 106:8
1366. One who stayed awake all night of Shavuos should immediately, at Alos Hashachar wash one's hands for Netilas Yadayim without a beracha, and listen to Birchas Hatorah from someone who slept, before one continues to learn. Shulchan Aruch 4:14, 47:12MB28
1367. Before Shachris one should use the restroom, wash his hands and then make the berachos of "al netilas yadayim" and "asher yotzar". Shulchan Aruch w/Mishnah Brurah 594:1
1368. One who stayed awake all night should not make a beracha on his tzitzis. Rather, he should make the beracha on his Tallis Gadol and have in mind to be yotze for his tzitzis with the same beracha. Shulchan Aruch w/Mishnah Brurah 494:1
1369. One who stayed awake all night should listen to the berachos of "Elokai Neshama" and "Hamaveir Shayna Mayeinoi" from someone who slept during the night. Shulchan Aruch w/Mishnah Brurah 46:MB24
1370. One who goes to sleep after Alos Hashachar Shavuos morning (or on any day) does not say the beracha of Hamapil. Shulchan Aruch w/Mishnah Brurah 239:1MB8, Piskei Tshuvos 494:5
1371. There is a well known minhag to bring flowers into shul and one's home as a remembrance that on Shavuos we are judged on "Peiros Ha'ilon" - fruits. However, one should not cut off branches from fruit bearing trees for this purpose because of the Torah prohibition of "Bal Tashchis". Shulchan Aruch w/Mishnah Brurah 494:3, Piskei Tshuvos 494:10
1372. There is a (not so well known) minhag to bring good smelling grass into shul to be passed around for people to make a beracha and smell the grass in remembrance of the Simcha of Mattan Torah at Har Sinai which was surrounded by grass. Shulchan Aruch w/Mishnah Brurah 494:3
1373. When practicing this minhag one should not pass the grass around during davening between Boruch She'amar and kaddish after Sh'mona Esrei because one is not permitted to interrupt davening at that time to make the beracha. Shulchan Aruch w/Mishnah Brurah 494:3
1374. Many have the minhag to eat a milchige meal (and milk and honey) on Shavuos. Some eat milchig at night and fleishig at the day meal, while others eat milchig, bentch, and then wash again, and eat fleishig to be yotze Simchas Yom Tov with meat.
Shulchan Aruch w/Mishnah Brurah 494:3
1375. If one eats milchig but not "hard cheese" (which requires one to wait six hours before eating meat) one need not bentch and wash again before eating meat. However, one should wash his /her mouth well and the tablecloth should be changed. (Other poskim require one to bentch).
Shulchan Aruch w/Mishnah Brurah 494:3, Piskei Tshuvos 494:12
1376. One should be careful not use leftover challah from a milchig meal at a fleishig meal. (This is applicable all year as well). Rather, one should use new challahs for each meal. This also fulfills the minhag of remembrance of the Shtei Halachem (Two Loaves) brought on Shavuos in the Beis Hamikdash. Shulchan Aruch w/Mishnah Brurah 494:3
1377. We read Megillas Rus on Shavuos because it was written to document the yichus of Dovid Hamelech and (according to one opinion) Dovid Hamelech was born and niftar on Shavuos.
Shulchan Aruch w/Mishnah Brurah 490:9, see also Shaarei Tshuvah 494:3
1378. For those who have stayed awake all night, the minhag of Sefardim is that after Alos Hashachar one goes to the bathroom, washes ones hands, (no al netilas yadayim) makes asher yatzar, Elokai Neshama, and Birchas Hatorah, as well as all the usual morning berachos for oneself. Kaf Hachaim 47:26, 46:49
1379. The minhag of Ashkenazim however is that after Alos Hashachar one goes to the bathroom, washes ones hands, makes al netilas yadayim, and asher yatzar, and then listens to and is yotze Birchas Hatorah, Elokai Neshama, and birchas Hamaavir Chevlei Sheynah, from someone who slept, and then one says all rest of the usual morning berachos for oneself. Shulchan Aruch w/Mishnah Berurah 47:MB28, 46:MB24
1380. While reciting Birchos Hatorah on Erev Shavuos, one may clearly stipulate that his berachos should be in effect only until the next morning. In this case, he may recite the berachos on Shavuos morning although he did not sleep. Keren L'David 59 and Luach Eretz Yisrael quoting the Aderes, Piskei Teshuvos 494:6
1381.If no person who slept is available, many poskim rule that the berachos of Elokai Neshama and Hamaavir Chevlai Sheynah may be recited even by one who did not sleep. Shulchan Aruch Harav 46:7; Kaf Hachaim 46:49; Aruch Hashulchan 46:13; Misgeres Hashulchan 2:2
1382. Some have the minhag to eat and drink more than usual on Isru Chag, the day after Yom Tov, as a commemoration of the time of the Beis Hamikdash, when those who had gone to Yerushalayim for Yom Tov were returning home with a happy and full heart. Some have the minhag to wear Yom Tov clothing on Isru Chag. Some also avoid doing business on Isru Chag. Shulchan Aruch w/Mishnah Berurah 429:2, Chasam Sofer on SA, S'U Torah Lishma/Ben Ish Chai 140, Darchei Chaim V'sholom 524, see Yerushalmi Mes Avodah Zorah Per.1 Hal.1
1383. Other reasons include; The Jews in Eretz Yisroel made Isru Chag into a semi-holiday in symmetry with the Jews outside of Eretz Yisroel who kept two days of Yom Tov, in order that the gentiles should not say that the Jews have different groupings, and this minhag eventually extended even to those outside Eretz Yisrel; The Arizal says that the day after Yom Tov still has some of the holiness of the Yom Tov. Sdei Chemed K'lalim1, Pe'as Hasadeh 154, S'U Torah Lishma/Ben Ish Chai 140
