Go to the indicated locations to find the corresponding side quest.
Go to the school. The designation of the Enterprise, "NCC-1701", can be found spray painted on the wall next to a classroom door.
Play Omar's side quest after the blow-up quest with Rahim. After escorting Omar he will say "And may the fish be with you, always".
Complete the following tasks to unlock PlayStation 4 trophy rewards.
During the "Bunker" mission, progress until getting the "Get Inside the Bunker" objective. Enter Town Hall and walk upstairs. Stand in front of the elevator (Screenshot). When the elevator door opens, a zombie that resembles a Clicker from The Last Of Us will emerge (Screenshot). You can kill it and loot the body (Video).
During the escort mission for Nick Pesto , he asks you to help him collect some items he lost. Note: You can find Nick tied up inside the back of one of Rais' trucks (Screenshot). One of those items is a ring. Nick says "One ring to rule them all" when he finds it (Video).
During the "Where's My Mother" side quest, to the northeast in the basement is some lotion in a basket. This is a reference to the killer in The Silence of the Lambs who passes lotion in a basket to the women in his basement .
There is a hidden area that contains a number of health packs, gauze/bandages, weapons, weapon boosters, and various other items. Do not attempt to go to there without a strong weapon. While in The Slums, move towards the northeast part of the map for the bridge. If unlocked, it is easier to start from the safe house under the bridge in that area. From there, hop in the water and you will eventually reach the first pylon area under the bridge. Hop back in the water towards the second one in front of you a disance. From there, hop on the concrete platform and go up the ladder to the left. From here, you are now inside the pylon supporting the bridge. Use the yellow pipes to climb up to a series of walkways. Note: The grappling hook will be useful. Eventually, you hit a platform that has a red door on one end. Open it and look down. You are now directly above a row of tents on the bridge. To get down, aim for the blue garbage bags and hop down. All the tents, trucks, chests, etc., all have something inside. Make sure to kill every zombie encountered, as they also carry valuables. Noe: If you cannot reach the red door inside the pylon structure, you can reach that location from the bridge itself by using the cables on one end to crawl up and down to the other side. This requires a very steady hand, and if you fall, you may land on the rocks and have to start over.