It is a common scenario where an introverted teenage boy (14-18) would shun socializing with girls, for varying reasons. Obviously, this is a self-reinforcing cycle (you can't get more skilled and comfortable with approaching the opposite sex without practicing it {reference: popular "Nerd Fitness" blog's series of articles on leveling up your social skills by Lindsay Miller}).
What are some practical steps that parents can take to help an introverted teenager to start trying to socialize, especially with opposite sex?
The advice should center specifically on overcoming the issues that cause an introvert to shy away from such an activity (to give an incomplete starter list: fear of rejection, fear of being made fun of, low self esteem, lack of awareness of HOW to approach someone, lack of conversational skills, high preference of solitary or nerdy activities, low existing social status among age peers, self perceived image issues).
Assume that the teenager is interested in socializing, but is unable to overcome his issues to act on that interest (as opposed to this question which asks about encouraging such an interest in the first place).
s/girls/boys/ if the teen is homosexual. But anecdotally, shy introverted teenagers are more susceptible to this than homosexual ones who are out of the closet... and clearly for the ones who aren't being shy isn't their main concern