Religious Beliefs
Aztec religion was the product of the people’s acknowledgment and fear of the forces of nature. They realized that nature could act as either a force of good or evil and in an attempt to personalize and constrain the elements; they created the gods and goddesses that ruled their world. The Aztec world originated not in a geographic sense but a religious one with the universe divided into a horizontal and vertical plane with each portion under the control of a different deity. The vertical plane consisted of thirteen levels of heaven and a varied number of hells with each level of heaven was occupied by a different god. The heavens were also divided into east and west based upon how a person died. The horizontal world was divided into Cardinal directions and the center, with each region falling under the control of a different god. North and south were considered fire regions with the north being controlled by the fire god, Mictlantecuhtli the god of death, while the south, which was viewed as a dark place, was controlled by Xipe (the god of spring and flowers). The east and west were considered water regions with the west being controlled by Quetzacoatl, the god of knowledge, and the east was controlled by the rain god, Tlaloc and the the cloud god, Mixcoatl.
Depending on what the people sought from the gods, their sacrifices varied in location and to which god the sacrifice was ordained for. Other forms of worship included self sacrifice where blood was drawn from the ears, tongue, or penis and burnt as an offering, or the offering of presents in lieu of a human sacrifice. People also prayed and performed other various acts to gain favor from their chosen god.

Because of the elaborate religious beliefs of the Aztecs, the priest had a distinctive cultural status. At an early age, candidates for priesthood would start training and devoted themselves to the preparation of being a priest. The priests would live their lives in celibacy, slept little and acted as the common link between man and the gods.

Aztec god of knowledge, Quetzalcoatl. Only 2 out of the 15 people polled were knew who Quetzacoatl was.

Death and burial practices
Like the Egyptians, the Aztecs believed that their earthly status and wealth transferred to the afterlife so nobles were buried with their positions and oftentimes slaves to serve them in the afterlife. To portray their earthly stature, nobles were either buried in a squatting position or cremated; they also sometimes buried women with noblemen to serve their desires in the afterlife. Treasure buried at the feet of the noble. When a child of stature passed away, they were buried with dogs, to ensure safe passage into the afterlife. The mother, and sometimes the father, of the deceased child would cut off one or more of their fingers and bury them on each side of the infant as a “symbolic attendant” for them in the afterlife.

Surprisingly, 1 person viewed human sacrifice as a viable religious practice, but we hope he was just kidding.

Human Sacrifice
Contrary to popular belief, human sacrifice was not purely religious in nature. It served the dual purpose of public reaffirmation of power and demonstrate the prerogatives of status. It was commonly a means of commemorating constructions celebrating victories of war, carried out at ruler’s initiative.) Human Sacrifice was an expression of political domination and was an instrument for intimidation and punishing disobedience.
In the capital city of Mexica, most of the sacrifices were captives of war, but were sometimes children depending on which god was being sacrificed to and for what purpose. While the locations for sacrifice varied between the central plaza of a town, altogether outside of the town, or on top of the pyramids that surrounded the plaza, they were always carried out of a sacred alter made of red rock like the one pictured.
People knew surprisingly little about aztec culture... is the texas education system to blame, or are the aztecs not viewed as an important historical topic in American history?
Traditional sacrificial knife.

Ceremonial costumes
There are two distinctive styles of traditional sacrificial Aztec clothing which consisted of loincloths, the long (past the knees) and the “knot”. Each style meant a held a different significance to the people, the long style was associated with religion and was the clothing of the gods, while the knot was associated with the secular world and was worn by the common mortal. Although it is not clear what the garments signified, it is clear that they were only utilized as special purpose attire. The Aztecs viewed religious costumes as a symbolic message that conveyed a greater meaning, and they believed that the traditional religious dress contained clues that reveal its homeland and the attendant connotations that area held for subsequent peoples
In preparation for religious events like sacrifices or holy days, Aztec priests might not cut or wash their hair, and they blackened their bodies with ashes cremated by poisonous snakes, insects and other animals.

Traditional headdress worn by priests.