[ Psychology ] Open Question : How do I open up around people? become more extraverted?

I've really never been close to anyone before and never really had any 'best' friends. I'm uncomfortable when people hug me or get to close to me emotionally. Slowly I've made myself one or two closer friends and they're completely honest and open about their problems, fears and what not. They assure me I am a very good 'listener' but I'm concerned they don't know much about who I really am and I'm unsure how to tell them. Sometimes it might seem like I'm pushing my friends away, but I'm not sure what else to do. So, what is the secret to being an extrovert? Sorry for the grammatical typo in the question, it's irritating me.