Store everything which you don't need in your workbench at the Red Rocket Station. Once your begin to reach your carrying capacity, jut go back to your workbench and dump all the junk, spare weapons or anything else you don't need.
As you will progress through the game you will find out what is more valuable and what less. For start, you can ignore empty bottles, tableware, things made of ceramics, glass rubber. Among more desirable materials are wood, screws, springs, circuits, cooper, adhesive, oil, hide, ballistic fiber. Generally more complex things are more valuable then simple ones. Say if you have space just for one more item and you can choose between typewriter and empty can, take typewriter. Use common sense.
You can view what materials item is composed of by selecting it in your junk inventory in your PIP Boy (you can't do it with armor and weapons, you need armor and weapon workstations for that).
You can put those pieces back anywhere by opening power armor inventory (R button on PC). You can do that at the power armor station at Red Rocket too by clicking on power armor station while having armor frame nearby.
Use "Radaway" (under Aid category) to get rid of radiation. Also consider using "RadX" before entering radiation areas since it raises your radiation protection and you take less radiation damage. Some equipment, like gas mask also raise radiation resistance.
Medicine perk will raise effectiveness of Radaway. It will also raise effectiveness of Stimpacks therefore it is useful perk to take early on.
Every word you see is potential password. When you click one of them, number of correct characters inside will be displayed (correct by both type and position).
Say correct password is "Dog". If you click at "Hog", number of correct characters is 2 (og). This can be used to give you clue to find correct password. You however have just 4 tries after which computer will lock you out for 10 seconds. Then you can start anew (with new password).
I generally tend to click first word then try to find the next one with number of matching characters computer gave me as a clue. Then next one which matches number of characters in the first and second words I selected. And so on.
There are also hidden character strings in the code. They are always encapsulated inside these characters: [] () {} <>
So if you see for example ($&%#@), click on ( symbol. Rest of the string will be selected automatically which is how you will know that it indeed is the hidden string) and two things might happen: either one of the false passwords will be erased or (which happens only rarely) number of tries will be reset back to 4.
Myself I usually try words first until I have but 1 try left. Then I go hunting hidden strings. Usually there is at last one which will resets the tries. Then I continue.
Early on best armor (except your power armor of course) is your vault suit and leather armor (made of 5 separate pieces). You should be able to scavenge leather armor pieces from raiders fairly early on. If you invest in to 1 level of armorer perk, you upgrade leather armor pieces to their maximum protection which will give you very solid protection for the early game.
If you search a little bit around Sanctuary, you can find military helmet which will be for long time best head armor you can find. Hint: search for signs of military activity to find it 
http://fallout.wikia.com/wiki/Fallout_4_weapons
Give it some time.
Scout ahead, don't just run around everywhere. Switch to sneak mode, climb that small hill in front of you or rock or car wreck which will give you nice overview and look around. Use scoped weapon as a substitute for binocular to scout distant places. Once you know what's in front of you, choose next elevated position on your path and go there. Repeat.
If you discover something which moves and want to find out if it's hostile or not, enter your "slow motion mode", which is called VATS. Hostile creatures and humanoids will be displayed in red, friendly in green. Friendly one can still turn hostile as a result of some actions, dialogue choices or similar, so always be careful. To be able to enter VATS you however have to come closer to your target. Use sneak mode.
If there is skull next to name of creature in VATS mode, that creature is well above your level and very dangerous. It can likely kill you in two-three hits. Same goes for creatures which have "legendary" in their name.
Some creatures are very dangerous even without scull or legendary prefix in their name. Use common sense and caution when deciding how dangerous they are. large cockroach will likely be less dangerous then mutated monster with large claws.
Once you know your enemy, you can decide to avoid it. You don't have to fight everything you encounter. game progress mostly through quests, so you will not miss anything. Once you decide to fight, try to draw at last rudimentary plan of your attack. Opening the fire without knowing next step is likely to kill you. Find advantageous position first, give orders to you companion, if you are up against group of enemies, decide which one you want to engage first. Have a escape plan if things turn bad. Lie down mines and so on.
Sniping from hidden position is one of the most effective ways to fight in Fallout. You should consider it if you are having problems. First of all you need decent sniper weapon. Early on, .45 pipe revolver rifle can be turned in to very good early game sniper rifle. You should be able to find .45 revolver in some form pretty early in the game. Mod it with hard receiver, long barrel, standard stock and small scope. You can do these modifications with any perks.
When sniping, always do it from "sneak" mode and if possible aim for head (or other vulnerable parts depending on creature). Hits in sneak mode do 2x damage and headshots do some extra damage as well. You can kill many early enemies (bandits, ghouls) in a single shot like this. Do it at the distance and if enemies start to discover you (you will see word [Hidden] turn in to [Caution]), move away behind some cover and wait until it changes back to [Hidden]. [Hidden] means that enemies does not know about you. [Caution] means they know you are there but did not see you jet and are likely looking for you (they will give up after some time). [Danger] means you have being discovered.
With enough patience you can kill whole groups of enemies like this without them ever discovering you. Just move away (still in sneak mode) in to cover and wait after each shot and then come back to shoot more.
Before you start sniping, make sure your companion will not give you up. Command him to stay back somewhere where he can't be seen by enemy. Come back for him later. Btw,you can command companion to stay from a distance. Just command him to go somewhere, when he arrives there, your cursor will change and you can command him to stay. You can recall him in the similar way.
You can always run away from a fight. Most of the enemies will give up chase after some time. In fact running away should be your first instinct when ever you are jumped by enemies unprepared. You always come back later while evaluating your enemy, with the plan of action and clear understanding what enemy you are facing.
Besides long range weapon, always carry some close range weapon with good firepower with you. Some encounters will inevitably gets more personal. 10mm pistol is good choice early on as is pipe rifle with automatic receiver and larger magazine.
Assign Stimpack to a hot key and try to always keep eye on your health bar. Use stimpack when it falls below 50%.
Jet and drugs made of jet like psychojet or bufjet (which you can craft) are very useful in a fight. Myself I assign one of them (I prefer psychojet) to hotkey and hit it any time I fell under great danger. It will slow time for 10 or 15 seconds and is incredible useful in difficult fight. Try it.