Shyness is not innate. We can experience shyness in various settings, typically more acutely in some than in others. Don't label yourself as a shy person. Your shyness is reversible, not a life sentence you must drag around with you forever.
Shyness tends to emerge when we suffer from self-image issues that make us overly worried about what others think. It can appear as lack of eye contact, stuttering, or inability to approach others. One technique to overcome shyness is to care less about what others think. The best method for addressing shyness is to leave your house more. Become more social. For example, join a group with similar interests.
If you're shy at work, strike up friendships with one or two co-workers whom you invite to coffee or lunch. Gradually expand the circle to more people. Interacting in a casual environment will help you be more comfortable sharing your opinions in meetings and cubicles.
To become less shy with the opposite sex, go out with your friends at night, and imitate them, if you feel uncertain. Go bowling or to a concert if not to a bar or a club. Practice being less shy by chatting up service workers who assist you at the cashier counter or the restaurant. They're paid to be nice to people -- you can start perfecting your conversation skills with them. They'll appreciate being treated like human beings, not robots.