Halachos Relevant for One Who Remains Awake the Entire Night of Shavuos
Many have the custom to stay up Shavuot night learning torah in anticipation of accepting the Torah on Shavuot. The Mishnah Berurah (494:1) quotes the Arizal who said that one who learns all night on Shavuos will live the next year without being damaged. One reason given for this custom is that Klal Yisroel were sleeping the night before the Torah was given and Hashem had to wake them up in order to accept the Torah. Therefore, we need to rectify this by remaining awake.
Certain brachos may be affected by one staying up all night. I will therefore do my best to clarify the relevant laws and customs for Shavuos morning. [Please note the following laws only apply if one stayed up the entire night. If one slept for a period of time during the night, the laws may be different, and a rabbi should be consulted.]:
Modeh Ani– One need not recite.
Al Netilas Yadayim– The poskim debate whether one should recite it. The Mishnah Berurah (4:28) writes that one should go to the bathroom prior to Davening and he may then say a blessing of Netilas Yadayim. Sefardim wash without a blessing even if they went to the bathroom. (Yalkut Yosef 4:8)
Birchas Hashachar (Except for Elokai Neshama and Hamaavir Sheina)- One must recite.
Elokai Neshama and Hamaavir Sheina– The poskim debate whether to recite them. It is therefore preferable to have someone who slept recite it for the congregation. If there is no one present who slept the custom of Sefardim and Chabad is to recite the brachos. The Aruch Hashulchan (46:13) likewise feels that one may recite these brachos even if one stayed up all night. It is unclear what the Mishnah Berurah would feel about this halacha and a rabbi should be consulted. It may be worthwhile for one who is Sefardic or Chabad to recite it for the whole congregation.
Birchas Hatorah– The poskim debate whether one should recite it. It is therefore preferable that one who slept recite it for the congregation. If there is no one that slept present one does not recite the bracha. If, however, one slept on Erev Shavuos (Shabbos afternoon) one may recite the bracha Shavuos morning. (M.B. 47:28)
Tallis Gadol– A bracha is recited.
Tzitzis (for those that do not wear a Tallis Gadol)- If one wore the pair of tzitzis all night one does not recite a bracha. It is therefore preferable that one who dons the Tallis Gadol to recite the bracha and have in mind to fulfill the obligation for those wearing Tzitzis.