Wharf District
After breaking through the doors into the combat zone, turn left and go to the end. A Boomer should come through a door to your right (which is the direction of the turret). Don't turn in that direction. Instead, turn left and you should see the COG Tag under an overhang next to a bulletin board.
Parade Grounds
As you get to the parade grounds, you'll come to a barrier you need to open. Before this, on the right side will be a structure that you can climb up with stairs. At the base of the stairs will be the Crimson Omen on the wall. Go up the stairs, turn right and then turn right against so you are just above the stairs. You'll find the COG Tags on a pile of rubble.
Upper State Street
After you deal with the first patrol, go past where they came from and you should see a relatively ruined building on the left side (this is where your waypoint is). Start climbing up the left side of the rubble and follow it until you can't go any further. You'll find the COG Tags tucked in here on the ground.
State Street Rooftops
After you clear out all of the Grubs and then a Reaver appears, there will be a wooden bridge that you can cross to get over to the domed roof tops and your exit. Instead, go up the stairs next to it. You'll find ammo on this platform along with a Longshot. Keep going down the end and watch on the left near the wall. Towards the end of this platform, you'll find the COG Tags on the left.
First Avenue Rooftops
Right at the start of the level, you'll see the Crimson Omen on the wall to your left. Go past the Crimson Omen and round the corner to the left. You'll find the COG Tags on the floor just around the corner.
Museum Square Rooftops
If you walk straight ahead and past the turret on the upper level, you'll see stairs leading down. Go down these stairs and you'll see a row of vents leading left. Follow the vents to the left and you'll find the COG Tags on the floor.
Overlook
You can't get these tags immediately. You'll have to wait until after the first wave. From your bunker that housed the turrets, go out the left door and then go right to find stairs. Go down these stairs and turn right. You should find a door that is now open on the far wall. Enter the building, go down the hall and turn left into the next room. You'll find the COG tags on the ground next to a hole.
