Pull your trousers up, tighten your braces up and trim your 'tache, because you need to be well presented in the Boston Wasteland if you want to get the most of of the people you come into contact with. Specifically, the higher your charisma, the more NPC dialogue options are opened up to you. You no longer have separate skills for persuasion and bartering, so it all rests on your charisma, which can be boosted by certain items and combinations of clothing. Sunglasses, for example, will give it a bump, as will certain hats and fancy suits. Something to be wary of is that if you're wearing a power armour or any other whole-head helmet, you won't get any of your other headgear charisma bonuses. Make sure to take off your helmet before speaking with the locals. Common courtesy goes a long way in Fallout 4.