With 2 days left in Frontlines....

Jambijon: Defending/Attacking the caps or objectives earn you a lot of points.  Also, try running inspire or Engineering to boost your points.  I will sometimes run inspire on a more mobile tank and try to buff as many as my allies as possible.  After you give them the buff, they will have it for 10 additional seconds after you leave. When your allies start dealing damage you'll rack up some good XP.