The Quarantine Zone - Beyond the Wall
Artifact #1-2: Boston Q.Z. Map, Military Pamphlet
These are automatically in Joel's possession once you collect your backpack.
Firefly Pendant #1
After climbing the ladder into the abandoned house, move through the kitchen and past the stairs to find a bedroom. On the desk in here is your first pendant.
Artifact #3: Note to Brother
Just after your first encounter with the infected, you'll head up some stairs. Before exiting the building, turn left and open the door. In this room, you'll find a note on the table near the window.
Firefly Pendant #2
Just after exiting the building with your first plank, Joel will tell Tess to check for soldiers. In the very next area, look up to spot this pendant dangling from a tree branch. Shoot it to drop it into grabbing range.
The Quarantine Zone - The Slums
Artifact #4: Drafting Notice
Just after moving through the bus, this hard to spot collectible will be on the ground near a table.
Artifact #5: Wanted Poster
Just a few steps past the previous artifact, you can spot this poster is attached to a storage unit. It too can be collected.
Artifact #6: Warehouse Key
You'll obtain this while learning about stealth kills. Once you hop into the office room and take out the thug, he'll drop the key.
Artifact #7: Shipping Manifest
Once you reach the wharf, Joel will automatically jump off the ledge and into cover. From here, move right to find this artifact near the railing.
Artifact #8: Dock Notes
Just before reaching Robert's office, you'll be in a dry dock. Head to the side of the suspended boat opposite the office to find this artifact behind a dumpster.
The Quarantine Zone - The Cargo
Firefly Pendant #3
Upon starting your travels with Ellie, head straight forward to find a dead body against a newspaper dispenser. This pendant is in its hands.