re: Fallout 4?

Save your useless junk in your workbench so you can use it for building. Sell weapons and armor you don't want. Might want to save crappy leather armor as you will need lots of leather for almost any armor mods you make. You can also give guns to settlers to use in case of attack. They only need one round of that ammo type to use the weapon.

Once you have the right perks you can build shops in your settlements and sell to them so you don't have to go one of the cities.