You have to actually like people, be present, and set down whatever stands between you and vibrant, pulsing reality. It's a lot more like practicing how to free fall than learning how to act in a movie.
The most charismatic people I know, who seem to have this radiant, magnetic quality to their presence, are actually those who actively invite you to things with your best interests in mind but are totally okay with you declining, and they really mean it.