Fast - The Torah states that this is a day on which Jews are to “afflict their souls” - by observing a total fast, abstaining from both food and drink. There is also a prohibition against all physical pleasures, wearing leather shoes, washing any part of the body (including brushing the teeth). The fast, which lasts from sundown on the eve of the holiday until the stars come out the following night, is intended to not only cause physical discomfort, but to relieve a person of involvement in physical matters so that he can concentrate on the prayer and spiritual introspection required on this day.
Kaparot - atonement ritual. On the day before Yom Kippur there is a customary atonement ritual, in which a live chicken is swung in circles above the head of a person, in the belief that the person’s sins will be transferred to the chicken, which is then slaughtered (the ritual is, of course, accompanied by special prayers). The chicken is customarily given to the poor or sold, and the money given to charity.
Selichot - asking for forgiveness. In addition to the prayers during the days of repentance preceding Yom Kippur, on the holy day itself or before it, it is customary to ask forgiveness from anyone whom one might have offended. According to Jewish belief, Yom Kippur atones for the sins between man and God, but not between man and his fellow man - people must grant one another forgiveness individually.
The meal before the fast - on the eve of Yom Kippur there is a religious precept to eat a holiday meal that ends before the beginning of the fast at sunset. The fast begins immediately after the meal.
Prayer - Religious Jews spend the whole of Yom Kippur day in synagogue devoting themselves to prayer. The prayers include a general admission of sins, and each person silently adds his own personal sins. One of the important prayers is Kol Nidrei - All Vows, named after the opening words of the first prayer, which cancels any vows that a person has made. It is customary to go to synagogue dressed in holiday clothing, and many people wear all white clothes, symbolizing purity.
The blowing of the shofar - At the close of Yom Kippur, the shofar - a ram’s horn - is blown to mark the end of the day of prayer and fasting.