Here's what you need to keep an eye out for:
Sniper scope and compass - You’ll find a crashed plane here with a sniper scope and, more importantly, a compass that will always point towards your next objective.
Kalash rifle upgrades - There’s a tiny outpost here where you’ll find some good Kalash rifle upgrades early on to increase damage and stability.
Ammo carrying upgrade and Tsar Fish room Key - There are some prisoners here you can rescue who will give you a key to access the room below (point 4) where you can find the night vision goggles. There’s also Ammo Pouches upstairs that let you carry more bullets.
Night vision goggles - The night vision goggles here you can access early via the key from the prisoners you find at 3 above, or you can get them as part of the mission to get the railcar after you kill the Tsar Fish.
Gas mask upgrades - There’s a small shack here full of fungus and spiders where you can find the Extended Filter, an upgrade that makes your gas mask filters last longer.
Throwable ammo upgrade - This gas station has a few bandits to take out. Kill them and explore inside to find the throwing weapon harness which lets you carry more knives, grenades and molotov cocktails.
Metal detector - There’s a metal detector here that will help you locate resources if you equip it to your bracer. Look for a broken down crane and it’ll be in a small rusted house in front of that. You’ll have to break the lock off to get inside.
Kalash rifle upgrades - There are some ruined buildings here that are basically pillars and beams. Look for some ramps and shipping crates that take you up to one of the beams and follow it around to find a ladder and an outpost. You’ll find a Kalash heavy stock, and long barrel and compensator for a big damage and accuracy boost.
Kalash rifle suppressor - The safehouse here has a Kalash suppressor barrel if you want some full auto silenced fun (it’ll cut damage and range but alert less people). There’s also another sniper scope if you haven't already got one.
Teddy bear - If you want to find the teddy bear for one of the side missions it’s on top of a big cylindrical gas tower here. Be careful because there’s a lot of radiation.
Guitar - If you want to recover the guitar for one of the side missions you’ll find it here atop a tower filled with bandits. There’s also a prisoner you can release.
Battery upgrade - There’s a Charge Controller here that will extend your battery life. You’ll find a large building with electrically sealed doors and a smaller shed with a generator. There’s a gas can around the back of the shed you can use to power up the doors and open them to retrieve the battery upgrade from… somewhere interesting.