Here is a list of things you should do to survive at the start of the game:

1) Do not fight: At the beginning of the game you'll have a stick and nothing else to fight your opponents, is better to avoid enemies by going around in stealth and scrounging loot from your surroundings without getting noticed by enemies, keep doing so untill you find a decent weapon, even a rebar (barely stronger than a stick) is a BIG upgrade for the following point.

2) Stealth engage is the key: ALWAYS start a fight 1v1 and by sneaking behind an enemy and hitting him in stealth, the enemy will be stunned, at this point immediatly exit stealth and start swinging your weapon untill the enemy drops.
If you get discovered RUN away, when the enemy drops the aggro (you can notice from the sound and when you crouch "hidden" will appear on the bottom of the screen) wait that he stops searching for you and try again.

3) Keep an eye out for herbs: Herbs are EVERYTHING early game, 2 herbs = 10% of your max health recovered, don't waste them for herbal tea or joints (yea you can craft joints xD).

4) Craft a backpack: You can craft a backpack anytime you want, open your crafting menu and click on the "armor" section once you gather the materials (really easy to craft) increase your carrying capacity by 10kg, after you craft it remeber to equip it.

5) Follow the quest untill you get your base: Don't start wandering around to get overburdened after 20 min, follow the quest and sooner or later you'll get your base, in there you can stash items without limit and sell items.

6) Don't get tricked by the game: When you open the inventory the game will have 2 sections "tools" and "random items" this is a bit misleading to a newbie, "tools" does mean only crafting stuff and "items" doesn't mean only selling stuff, you will need a lot of items to repair benches and quick travels so don't sell everything to regret it later. Is better to sell only broken weapons or weapons you are not interested in.

7) Always bring a gun: Sooner or later you will stumble upon a gun, don't waste it! Guns are extremely powerful and can really save you when you're in the middle of nowhere with your legs broken (litterally), so always pack some heat and use it sparingly.
Remember to always take the first shot in stealth, stealth hit with guns stun too, so sneak up on a tough enemy, shoot him in the head and then shoot him again, if they survive with a little of hp don't waste another bullet, wait for them to start running for healing and when they stop smack em dead.

8) Upgrade the medic station asap: The second lvl of the medic station (is the max lvl too) will let you heal for free and remove all your traumas, is a must have!

Now you should be ready to explore this alien wasteland without quit raging due the countless traumas you racked up by charging anything you see. Have a good time survivng!!!