How to tell if a guy likes you? Do you think he does?

Ok, so there's this guy that I've been friends with for a long time. We live in the same place, and since I have a twin brother, he is like BEST friends with him (and I). So, yesterday, I was walking my dogs and he came over since I was having trouble with them, and offered to walk them. Then, we started talking. I like him, but I don't know if he likes me. We got into this whole conversation about couples and then he got all nervous and started talking about something else. So, what do you think? What should I do? ~ Thank you in advance ~