Some have the custom on the night of Yom Kippur, to read the entire book of Tehillim (Psalms). During the day they read it again for a second time. It is an important סגולה (Seghullah - protection) for the atonement of the soul and to nullify all harsh decrees.
When reading the Tehillim, one should read them from start to finish without any interruption, with the Ta'amim (tune) and in a pleasant manner. When one reads them correctly, one creates an angel who will act in the person's defence.
It is good for the men to recite the first four chapters of Tehillim, after 'Arbith. They should also endeavor to study some Torah, before going to sleep, so that they will fall asleep in the midst of words of Torah. Additionally, in the Synagogue, it is good to read Adra Rabba and Zota, as well as the Mishnah and Gemara of Yoma. If one does not read them in the Synagogue, they may also be read at home.
(See Maamar Mordekhi [Eliyahu], Hagim, 46:64, 65, 66)
Yom Kippur, Yom HaKippurim, Tehillim,