Beliefs about the transition from the mortal world to eternal life were recorded more than five thousand years ago on the basis of the shamanic practices of earlier tribes. New ideas were incorporated from time to time, but the rituals and beliefs were transmitted in the most immuable way by the Egyptian priesthood. From what we know, egyptians people lived in a world of popular superstitions mixed with higher philosophy and occult practice. Most important for full participation in the afterlife was the need for an individual's identity to be preserved. Consequently, the body had to remain intact and receive proper funeral rites as well as regular offerings of food and drink. The necessity to preserve the body is very central to the myth of Osiris.  As the hawk arose from the dismembered body of Osiris, so would their awareness survive the bodily death. All ancient Egyptians believed in the afterlife and spent their lives preparing for it. Pharaohs built the finest tombs, collected the most elaborate funerary equipment, and were mummified in the most expensive way. Others were able to provide for their afterlives according to their earthly means. Regardless of their wealth, however, they all expected the afterlife to be an idealized version of their earthly existence.

The final step in the transition to the afterlife was the judgment in the Hall of Maat (the god of justice) by Horus (the god of the sky) and Thoth (scribe of the dead) by comparing ab (the conscience) and a feather. The ritual was known as the Weighing of the Heart. Heavy hearts were swallowed by a creature with a crocodile head who was called the Devourer of Souls. The good people were led to the Happy Fields, where they joined Osiris, god of the underworld. Many spells and rituals were designed to ensure a favorable judgment and were written in the papyrus or linen "Book of the Dead."

Life after death was thought to be a natural continuation of life on earth.

the Egyptian version of existence in the afterworld is somewhat obscure. In certain instances it seems that the Egyptians actually believed in a physical existence after death for which the departed required worldly riches and sustenance.

The following testament comes from the pyramid of Unas, a 5th Dynasty king:

The heavens drop water, the stars throb, the archers go round about, the bones of Akeru tremble, and those who are in bondage to them take to flight when they see Unas rise up as a soul, in the form of the god who liveth upon his fathers and who maketh food of his mothers. Unas is the lord of wisdom and his mother knoweth not his name ...The kas of Unas are behind him, the sole of his foot is beneath his feet, his gods are over him, his uraei are upon his brow, the serpent guides of Unas are in front of him and the spirit of the flame looketh upon his soul. The powers of Unas protect him: Unas is a bull in heaven, he directeth his steps where he will, he liveth upon the form which each god taketh upon himself, and he eateth the flesh of those who come to fill their bellies with the magical charms in the Lake of Fire.

Osiris

At the height of his reign, Osiris is murdered by his jealous enemy Set. His body is enclosed in a chest that is placed at the mouth of the Nile, but eventually recovered by Osiris' wife, Isis. Set however, finds it once more and dismembers it into fourteen pieces he scatters throughout the land.

Isis searches for the pieces of Osiris' body and finds all of them except the phallus. At this point, Horus, the sun, the hawk god, appears on the scene. As the god of the sun, he always existed. In fact the hawk is probably the first living thing worshipped by the Egyptians, yet he is conceived by Isis from the dismembered body of Osiris lacking the progenitive organ! The appearance of Horus represents the resurrection of Osiris. Filled with his father's spirit, he defeats Set in battle.

More about Osiris