Complete Mass Effect 2 twice, or complete it once with a character imported from Mass Effect 1

Use the Omega 4 Relay

Obtain geth technology

Gain the loyalty of the biotic Convict

Successfully recruit the Justicar

Gain the loyalty of the Assassin

Gain the loyalty of the krogan

Gain the loyalty of the Professor

Successfully recruit the Assassin

Successfully recruit the Quarian

Complete a mission discovered by scanning an unexplored world

Successfully recruit the biotic Convict

Successfully recruit the Krogan