How can I tell if my best friend "likes" me?

Me and him have been friends for over 8 years. Everyone always says that we're gonna be married one day or that we should date, but we both say something like "Never" or "Ewww" (of course, we're not actually being mean to each other when we say that.) Anyway, I wanted to know if maybe those people are seeing something I'm not seeing. What are somethings I can look for?