In order to earn this achievement you need to speak to 50 citizens of Hope County. This should unlock through natural gameplay, but you can speed up the process by making sure to talk to everyone you meet. Anytime you see a store owner, talk to them in addition to any shopping. Anytime you liberate an outpost, talk to the people who spawn afterwards (they might give you side missions!). Anytime you meet a main character via cut scene, talk to them afterwards. Talk to EVERYONE!
Note: This achievement may be buggy. Multiple players have reported it not popping when it should have. Please add a comment if you've experienced something similar.