In assessing my War Assets from the Normandy's war room, I'm already seeing the results of my decisions in past games.
For instance, the First, Third, and Fifth fleets are at diminished strength after saving the Council from Sovereign in Mass Effect 1 (Paragon Ending), and the Marine 103 division is at reduced strength because I did not complete The Arrival DLC in Mass Effect 2.
What decisions in the past two games directly affect War Assets in the third?