-In the mission "Ambush", get to the end where you need to order one of your teammates to defuse the bomb. Order him to do that and stand beside him. He will complain about you standing next to you. Have your other person regroup and tell him to throw a grenade at the door in front of the bomb. You should get two kills. Next, look above you to see a person about to go on the turret. If you kill him, he keeps respawing. This is an easy way to boost your Assault points or any other desired A.C.E.S. points. Note: You will get more A.C.E.S. points under the Realistic difficulty setting.
-In Story mode under the Realistic difficulty setting, there is a glitch on the "Ambush" level. Proceed to the first bomb you encounter and tell your team to disarm it. While they are doing that, plant a C4 on the right window in front of the bomb, then turn left, look up top on the turret, and detonate the C4. You will see the enemies respawn. Continue killing them. They will keep respawning, allowing you to get an enormous amount of experience and A.C.E.S. You can do this as long as desired. Get an LMG for more ammunition. When you run out, restart the checkpoint.