You need to force yourself to talk to people, no matter how intimidating, go to as many social events as possible and mingle. I was very shy and after I graduated college and got my first job, I was thrown into all this social stuff, presentations, speaking in fornt of executives. I was prett much forced to get over it and it worked. I don't consider myself shy anymore - most peopel say I'm rather outgoing.
Another thing might be self-esteem. If your self-esteem is low you have a higher chance of being shy. Get over it.. nobody's perfect. If you're confident, others will overlook your imperfections.
Another thign to keep in mind is that shyness can often tmes come off as being snobby or the "i'm to good to talk to you" types...
There is no need ot be shy... you're not an alien among humans--- you're just like everyone else so relax and be yourself, stop caring what people will think or worryign over little details.