I have run a few games over the years, and a few were successful and a few more weren't. I play with the same five people every time, who I have been friends with for years, and this makes it difficult sometimes because we're all too comfortable with each other. We don't really get into the characters, we don't do voices, they don't really try to interact with the NPCs, and above all else they don't interact with each other. How can I turn this around. How can I get my friends to really fall into my world, without telling them to, which of course doesn't work.

I need sources, websites, books, anything like this would help. I have never followed a format. I wing every RP every time. I have been creating my own world for nine years now, which I originally tried to use to write books. Since I quit that, it's been a fantastic tool for role playing, but my friends don't have the same connection to the world as I do, for obvious reasons. How can I immerse them? How can I naturally get them to enter the world, enter their characters, and interact with it all?

Long winded responses are welcome, I'm not shy of reading. Please help me advance my skill, i know I have potential here. Thank you very much.