What helped me in my experience is having a very social friend. Not only will he put you in more social environments where you can practice your social skills, but he'll also teach you directly AND indirectly (meaning that you can learn a lot just by watching him socialize with others) how to confidently talk to new people. So try to find someone much more social than you and hang out with him sometimes. Also if you want to be confident around people you don't know, just improve yourself. One of the problems you might be facing is putting them on a pedestal or thinking that you're "not enough" to be liked by them. If you improve yourself you'll naturally gain the confidence to know that you're not below anyone and that other people's judgement doesn't matter. Hope this helps