This is a video/text guide to unlock the Pull Harder achievement in Titanfall, for 25g.
To unlock Pull Harder!, you must kill an ejecting pilot with the plasma railgun.
The Plasma railgun is a Titan weapon that is unlocked at level 12. This achievement can be made easier by killing 10 enemy Titans with it to unlock the instant shot mod, then equip this.
Basically, when a pilot ejects you want to lead your shot (depending on his direction of travel) and try to estimate where the pilot will be when your shot lands.
I made a video that shows it better than words. -