Simply win 50 matches of Capture the flag game mode. Some tips for it:
- In order to score the most points, focus in game type related actions instead of going into a killing spree, since they are the ones granting you (and your team) the most points.
- Avoid enemy titans (or any confrontation, actually) as much as you can.
- This is a team mode, so most of the time it's better to act as a team. Support your teammates carrying the enemy flag or defend your own flag against enemies.
- You can't keep the flag while riding your titan, but you can hop on to a friendly titan.
- Use the environment to speed you up by running the walls or using the zip lines.
The amount of points granted for game type specific related actions are:
-
Flag Capture (capture the enemy's flag),
400 points.
-
Flag Capture Assist (teammate captured the flag you dropped),
100 points.
-
Flag Return (return your team's flag),
100 points.
-
Flag Carrier Killed (kill the enemy pilot carrying your team's flag),
100 points.
Source: http://titanfall.wikia.com/wiki/Capture_the_Flag