While endeavoring on his personal goal of being more human, Data is indispensable to the Enterprise, serving as its second officer and chief of operations.
Blind since childhood, LaForge uses his impressive technical knowledge as Enterprise's Chief Engineer. He originally joined Enterprise as helmsman, LaForge is promoted in TNG's second season.
After his parents were killed in a Romulan massacre, Worf was raised by humans and became the first Klingon in Starfleet. He was promoted to Chief of Security in TNG's first season, following Tasha Yar's untimely death. Worf later leaves the Enterprise to join Deep Space Nine.
William T. Riker
The ambitious Commander Riker who aspires to make captain by 35 is the Enterprise's first officer.