Talking gives a very small friendship bonus, almost non noticable, but it does a tiny bit. The key is giving gifts. You can talk to anyone while holding anything, and you will give them the thing you're holding as a gift. Each person likes different things, and will respond if they like it or not. You can track who likes what by clicking on their profile in the social tab ( ❤️ icon). It'll track what items you gave them and what their feelings on it were.

Also there are items you can discover, and also conversations with others that will clue you in to what some people like.