If you play conquest you get 150 points for a base capture and i think 75 for capturing with other players. If you play rush you can get a lot of points by planting the bomb. I think the best way to rack up points is to play as a medic, unlock the healing packs and defibrillators and heal people. Each class has its own specialization that can earn you points. Assault has ammo packs that you can throw to your team , engineer can repair tanks/helos, medics heal people and snipers have C4, mortar strikes etc. Each has to be unlocked.