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

Use the Omega 4 Relay

Gain the loyalty of the Professor

Thresher Maw defeated

Gain the loyalty of Archangel

Obtain geth technology

Gain the loyalty of the Cerberus Officer

Successfully recruit the Justicar

Gain the loyalty of the Cerberus Operative

Successfully recruit the Quarian

Successfully recruit the Krogan

Gain the loyalty of the thief

Gain the loyalty of the mercenary ("Cerberus Pack" downloadable content)