Upon going to sleep:
Requirement to sleep: One is required to sleep at night of Yom Kippur in order so he can concentrate during prayers the next day and not fall asleep in middle.
Sleeping in Shul: Although it is forbidden to sleep in a Shul throughout the year, nevertheless on the night of Yom Kippur the custom is to allow doing so if one intends to pray throughout most the night or guard the candles from catching fire. One should not sleep by the side of the Shul which the Ark stands rather he should sleep on the opposite side or by the women’s section if there are no women there.
Saying Tehilim: Before retiring to sleep one should say the first 4 chapters of Tehilim as protection from ‘Keri’. [In the Siddur these four psalms are printed to be said immediately after Maariv and is followed by mourners Kaddish.]
Kerias Shema Shel Hamita: One says Kerias Shema Shel Hamita in the same order as said on other festivals, adding however the next nine chapters of Tehilim. (Chapters 124-132)
Not to cover oneself fully: It is proper to beware not to wrap oneself within blankets in order to avoid coming to nocturnal emission. At the least one should leave his legs uncovered as did Boaz, in order to avoid coming to nocturnal emission.
 619/15 and 18
 So is implied from Admur in the words “As songs and prayer is being said in the Shul throughout most of the night.” And “If one does not plan to say song and praise he is not to sleep in the Shul”.
 The reason: This is permitted being that the sleeping is being done for the need of the Shul. [ibid]
 Sefer Haminhagim p. 124