Chapter 2: Desperation (5)
1. Doctor's Journal - After you first run into Locusts in the hospital, you will find yourself on the second floor balcony. You should see a sign that says "Surgery" that points to the left. Follow the sign and the first room you come to on the left should have the collectible inside.
2. Jacinto Medical Center File - After heading down some stairs, you should see two U-shaped reception desks in the middle of the room. Between the two desks, you will find the collectible.
3. COG Letterhead - After heading into the next section of the hospital after the open courtyard, you will eventually find yourself in the cafeteria. Directly across from the entrance, you should see some blue double doors. The collectible is inside that room in front of the desk. [If you've picked up all of the collectibles up to this point, you should have just unlocked the "Collector" achievement.]
4. COG Proclamation - On the second floor of the hospital lobby, don't follow the stairs down yet and instead head to the right. You will eventually come to a dead end with an ammo box and the collectible.
5. COG Tags: Private Dylan Murphy - As soon as you exit the hospital, immediately take a right. The collectible is on the ground behind the pillar. This is actually the first one I missed on my collectibles hunt, so don't feel too bad if you overlooked it.
Chapter 3: Rolling Thunder (2)
1. Grindlift Notice - As soon as the level starts, do a 180 and it's right there next to the ladder.
2. Munitions Requisition Form - Part of the way through the level, you will disembark the Derrick while Dizzy repairs it. Immediately head to your left and you will see 2 ammo crates. The collectible is lying on the ground nearby.
Chapter 4: The Big Push (0)
There are no collectibles to be found in this chapter.
Chapter 5: Roadblocks (4)
1. Jacinto Sentinel Newspaper - When the chapter first starts, you will have to break down the door to the first building you see. Once inside, head up the stairs and you will see the collectible on the floor near some grenades.
2. Memorial Inscription - After fighting Tickers for the first time, you will have to chainsaw your way through a wood barricade. Immediately afterwards, you will see some tombstones on your right, as well as a large plaque on the wall -- this is your collectible.
3. Landown Delivery Driver's Note - After Cole shows up and takes out the Troika, head into the gas station and into the back room. The collectible is on the floor just around the corner.
4. COG Tags: Private Samuel Lee - Partway through the tunnel, your path will be blocked and you'll have to find a way to go around. There will be some stairs on your left, but immediately before the stairs is a small room with your collectible inside.
Chapter 6: Digging In (0)
There are no collectibles to be found in this chapter.