Dean-
Dean loves hearing you talk about random stuff, he loves hearing you ramble. He really likes the sound of your voice so he doesn't mind hearing you talk. You talk about your family, where you wanna visit, what you wanna do later on in life. It can be you telling funny and happy memories from your childhood or you being upset or worried about something and talking on and on about it till it's out of your system.
Sam-
Sam loves it when you scrunch your eyebrows, crinkle your nose and bite the inside of your lip when you're confused, worried, scared, when your watching a movie, talking, or even reading a book. That face you make, makes him smile.
Castiel-
Cas loves it when you ask him questions. Sure he doesn't know a whole lot about the human world and gets confused easily but you ask him questions about god, heaven, other angels and what it was like. Dean and Sam both think that the both of you are two very curious people.