Enlil is a prominent deity in the Mesopotamian pantheon, specifically in Sumerian and Akkadian mythology. The Anunnaki are a group of deities in ancient Mesopotamian cultures. It's important to note that these myths and religious practices evolved over a long period of time, and interpretations can vary.

Enlil: Enlil was considered the god of wind, air, earth, and storms in Sumerian mythology. Over time, he became a major deity, associated with the concept of "lil," which refers to the air and the space between heaven and earth. Enlil was often depicted as a bearded man wearing a horned cap, symbolizing his authority. His chief temple was in the city of Nippur.

Nippur: Nippur was one of the most ancient and important cities in ancient Mesopotamia. It was a center of religious worship and scholarship. The E-kur, or Enlil's temple, was located in Nippur and played a crucial role in the religious and political life of the region.

Priests of Nippur: The priests of Nippur were responsible for the rituals and ceremonies conducted at the E-kur. They held significant influence in the political and social spheres of Sumerian society. The high priest of Nippur was often considered one of the most powerful figures in the land.

Actual Practices: While specific details of the religious practices and rituals can be challenging to pinpoint with precision, some general aspects of Mesopotamian religious practices include:

1. Prayer and Hymns: Priests recited prayers and hymns to invoke the favor of the gods. These texts often praised the gods' attributes and recounted their mythological exploits.

2. Divination: Priests were often involved in divination practices, using various methods to interpret signs and omens to understand the will of the gods and make predictions about the future.

3. Festivals and Celebrations: Various festivals and ceremonies were held throughout the year to honor specific deities. These events often involved elaborate rituals, processions, and communal activities.

4. Role in Society: Priests held considerable influence in ancient Mesopotamian society. They not only performed religious duties but also played roles in education, administration, and even served as advisors to rulers.

It's important to approach these practices with the understanding that our knowledge is limited, and interpretations may vary among scholars. The details of religious practices would also have evolved over time and may have differed across different city-states in Mesopotamia.