Important NPC's (red color):
1) Lebiediew - He's the leader of this camp, as well as of Clear Sky organization. This man will grant you with a decent number of main quests.
2) Nimble - You can ask him a few questions the first time you meet him, concerning your current situation or the swamps. He can also tell you about the new functions of your PDA (short tutorial video).
3) Professor Tyczkow - You can to talk to him to find out some very interesting facts about the Zone.
4) Assistant Professor Suslow - First of all, you can trade your items with him. Suslow will also give you rewards for completing tasks for Clear Sky organization (mostly subquests).
5) Grey - He's the bartender around here. You can ask him for gossip or you can trade with him.
6) Frigid - He's a mechanic, so you can ask him to repair or upgrade your equipment. You can also ask him to grant you with a few subquests. If you find plans for new equipment and deliver them to him, you will be given some money.
Important areas (green color):
1) Campsite - Clear Sky - This is where you'll start the game. You should know that you don't have to worry about encountering any anomalies or monsters while you're inside the base. Also, using guns is strictly forbidden here. You can't reach the campsite later on by walking towards it, because it's supposed to be hidden. As a result, you will have to talk to one of the guides in the swamp area and ask your new ally to go with you.
2) Guard post - You'll visit this area only once. This occurs when you try to complete one of early quests for Lebiediew. You won't have to spend some additional time trying to explore the area, especially since there are some boars here and they could injure you.
3) Small field - You can ignore this area if you want to. The only exception is when you'll be presented with a possibility of completing a subquest here. Be careful, though. The area is very dangerous. You can encounter boars or renegades here, so it's very easy to die as a result of their attacks. Thankfully, some of your allies from Clear Sky should provide much needed support.
4) Observation tower - Just as before, you'll want to visit this location only to complete one of the subquests (maybe even more than once). It's even more dangerous here, because renegades tend to use staircases to shoot their targets from upper levels of the tower. You can follow them, however prevent them from surprising you.