Practice Practice Practice Practice Practice. You have to go out of your way to hang out with people to get any good at being fun to hang out with. WARNING: This does not mean you have to spend time at loud parties or bars or clubs. While they pretend to be areas for socializing, they're not really. It's one thing if you enjoy dancing or drinking, but places that are less loud and crowded are a lot better for conversation.
Practice Practice Practice Practice Practice. You have to go out of your way to hang out with people to get any good at being fun to hang out with.
I've done this and it didn't really work. Maybe it worked a little, but not at a very fast rate. To be honest, I think reading a small amount of social skills stuff and thinking about how to solve the problem a little helped much more than all the "practice" I've done in the last year or so.
Obviously you can't take this to the extreme and expect that you can instantly go from Michael Cera to Casano...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.