As was said: Learn to shoot. It's no different than the MG-armed WW2 birds: effective gunnery is a combination of range, accuracy, the size of the hit zone, and what you hit. Scatter your fire all over the enemy and you're just leaving a bunch of little holes, which requires a LOT added up to do any damage. Fire from extreme range, and the rounds that hit have less energy and will inflict less damage. Aim at the rear of his fuselage, and you might tear up the surface skin but will have little other effect (although having control cables that can be cut will make a difference, now).
Fire at close range. Not only will this improve your accuracy, but your rounds will hit with greater energy. The limited firepower of these guns means you NEED to shoot close. You can't pretend they're cannon.
Concentrate your fire. Don't spray all over your target. Pour your fire into one point and it will maximize the damage of the hit.
Aim for something vital. Hitting the pilot or fuel tank is the best target against these birds. You can aim for the engine but your guns may not have the power to cause significant enough damage to knock them down. Aiming at the wings is somewhat less useful against these birds, but taking off one wing, leaving just the three (in the biplanes) CAN make lining up for a more decisive hit much easier.
If you don't have a clean shot and have to take a snapshot, fire short bursts to conserve your ammunition for the sure tracking shots.
Last night at one point I had 3 kills in a Camel, and still had about 175rds/gun left when I went down (stupid collisions....)
