Tell others about what you think is a high priority tip for you in decision. Maybe you can tell them that never recon a area with too much zombies or say that the shotgun is better than the machine gun. Share your tips. This shall really help your mates and guess what? Earn AP by posting too.
I don't use machine gun a lot in Decision. I usually use rocket launcher and grenade. I switch those weapon while loading other. So I kill a lot of zombie.
I like te mechine gun, although it doesnt do much damage, but its good for drawing back the enemy such as the boss
The rpg7 is the best weapon in the game. You should always build a tower and factory in every map area you unlock. Instead of exterminating all the zombies on foot, go into a guard tower and with a machine gun, kill them all there.