Say the Kiddush for Shalosh Regalim, inserting the addition for Shavuos where indicated, followed by Shehechiyanu.
When after the Yom Tov meals, we say Yaaleh Viyavo and the Harachaman for Yom Tov. (See below, “Hosafos,” for the laws that apply if you forgot to say Yaaleh Viyavo.)
We stay up the entire night, reciting Tikkun Leil Shavuos and learning Torah.
The Rebbe Rashab once announced: “I have a manuscript of the Mitteler Rebbe in my possession, in which he promises that whoever stays up on Shavuos for the entire night will merit to receive the crown of Torah” (Toras Shalom, p. 3).
The Rebbe pointed out that many editions of the Tikkun contain certain mistakes, and he indicated the correct version that should be said (see Likkutei Sichos, Vol. 28, p. 315 for the details of these corrections).
If you did not finish saying Tikkun Leil Shavuos at night, finish it the following day.
It is customary to immerse in the mikvah shortly before alos hashachar.
If you were up the entire night, at alos hashachar use the restroom, wash negel vasser, and recite the morning berachos.
It is preferable to sleep a bit before davening, to enable proper concentration.
The Frierdiker Rebbe relates that in Lubavitch they would not say Krias Shema Al Hamitah tonight.
