Medic is the best class for getting points, by far.
Also, don't snipe if there's already three or more snipers on your team. And automatically choose Engineer when starting out on vehicle-oriented maps. And don't camp at the UAV. And go for the objectives. You'll get more points that way.
Hit the back button to spot enemies. Do that a lot. If you move your crosshair around slowly and keep pressing it, you'll probably spot a few enemies you didn't know were there. And do this every chance you get, and check nearly everywhere.
Also, don't snipe if there's already three or more snipers on your team. And automatically choose Engineer when starting out on vehicle-oriented maps. And don't camp at the UAV. And go for the objectives. You'll get more points that way.
Hit the back button to spot enemies. Do that a lot. If you move your crosshair around slowly and keep pressing it, you'll probably spot a few enemies you didn't know were there. And do this every chance you get, and check nearly everywhere.