The answer, I believe, lies in self-confidence. I know perhaps you're looking for a specific solution, but the truth is, as has been already answered in this forum, that "charisma" comes from within. Be friendly, express interest in others, smile, work on your physical appearance, work on your spiritual and mental development, exercise. One thing in particular might not be effective, but when you decide to develop in every way possible, you'll see how others will be attracted to you. A good tip is to act in a confident manner and always carry a positive attitude. You may feel silly at first, but the physical act of expressing confidence (by standing up straight, smiling, speaking assertively, etc.) has been proven to actually create self-confidence.