1. Talk to the merchants
Merchants are extremely useful in the game. You can talk to them to buy rare items, get new outfits, and shift unwanted scrap. They also sell maps that let you see where specific collectibles are located.
Pretty much every merchant has a unique set of items, so set aside some time to look at what's on offer. You can find them in most major settlements and sometimes in the wild near campsites. Their presence is marked on the map by a pair of antlers.