Sources : brkbeatjunkie and Nvidia's guide

You'll need Nvidia inspector to enable these settings : http://www.techspot.com/downloads/5077-nvidia-inspector.html
There should be a similar alternative for AMD, but I haven't researched it.

ANTI ALIASING (AA)
Read this article to enable SGSSAA anti aliasing (works for ME1, ME2, ME3) : https://www.geforce.com/whats-new/guides/mass-effect-3-tweak-guide#8
For other games, check this document : https://docs.google.com/spreadsheets/d/1ekUZsK2YXgd5XjjH1M7QkHIQgKO_i4bHCUdPeAd6OCo/pub?output=html
There's a good explanation of the differences between AA techniques, too.
Recommended values :
0x080000C1 (ME1, ME2, ME3)

AMBIENT OCCLUSION (AO)
To force HBAO use this document to find the HBAO flag for the game you want to add AO to : https://docs.google.com/spreadsheets/d/1sq0vgFlerS-YT093TS2jEpx6xjZP7X1x1BcAs7EHXYY/edit#gid=0
Then follow this picture to add the flag in Nvidia inspector : https://u.cubeupload.com/MrBonk/Inspector.png
Lastly, disable AO in the game's settings so that only HBAO is running, not the default game's AO.
Recommended values :
0x0000002F (ME1, ME2)
0x00000020 (ME3)