The only thing I know is that one must place a coin under the tongue to pay Charon, the ferry man of the Underworld.
The Greeks believed that at the moment of death the psyche, or spirit of the dead, left the body as a little breath or puff of wind. The deceased was then prepared for burial according to the time-honored rituals. Ancient literary sources emphasize the necessity of a proper burial and refer to the omission of burial rites as an insult to human dignity (Iliad, 23.71). Relatives of the deceased, primarily women, conducted the elaborate burial rituals that were customarily of three parts: the prothesis (laying out of the body), the ekphora (funeral procession), and the interment of the body or cremated remains of the deceased.
After being washed and anointed with oil, the body was dressed and placed on a high bed within the house. During the prothesis, relatives and friends came to mourn and pay their respects. Lamentation of the dead is featured in early Greek art at least as early as the Geometric period, when vases were decorated with scenes portraying the deceased surrounded by mourners. Following the prothesis, the deceased was brought to the cemetery in a procession, the ekphora, which usually took place just before dawn.
Very few objects were actually placed in the grave, but monumental earth mounds, rectangular built tombs, and elaborate marble stelai and statues were often erected to mark the grave and to ensure that the deceased would not be forgotten.
SOURCE: Death, Burial, and the Afterlife in Ancient Greece, Department of Greek and Roman Art, The Metropolitan Museum of Art, October 2003