This is a pretty simple achievement when you play through a lot of the levels. The titans are pretty dumb and once you are latched on, you can easily maneuver yourself to a point where you can see their napes. Two good tips for doing this quickly are to use your allies to damage titans that are in your way to prevent you from taking the damage, and to head straight for the main objective. This will end the level and activate the final subjugation target pretty quickly, meaning that if you are to fail, its easier to repeat and faster to gain this achievement.