I don't know about charisma...but I certainly seem to hog the limelight compared to a few years ago. I was a totally reserved person but I got no peace or security in my reserved form so I decided to try and 'turn on' my charm. I'm very observant so I subconsiously copied the most 'charismatic' people I knew (Charismatic is a controversial word, it can mean different things). Anyways I would turn it on and off and then it became more on than off, and I soon became the person I was trying to be (even though it wasn't me at all!!), then I developed my own unique style and today I steal the limelight without wanting to. And its sometimes really annoying because I have to watch my every move and sometimes I lose my composure.
But compared to what I was before I think the most subtle changes include always smiling (I don't even notice that I smile it just comes to me), witty comments, not esentially jokes. You don't have to be a good comedian to get the people around you with a smile on their faces. Make humor-based reactions to expression, to a sentence. Sarcasm is an important tool in this.
I sometimes lose my credibility by overdoing it with humour so you have to make sure you're not always goofy or you'll be labelled that way.
In fact always engage in a good intelligent debate but make sure you win. The most important thing in an arguement is to NEVER EVER shout at the person, let them shout at you. The person who is shouting is the person who is losing the arguement and needs to shout to heighten his point and tries to influence others by his volume not by his reason.
Another trait I have is that I'm relaxed. I didn't develop this so I don't know how you get it. I was always an EXTREMELY relaxed person. I always feel cool and I'm hard to wind-up. I never lose my cool.
Posture, keep yourself straight and always assume the leading position. If you're walking with someone, NEVER let them lead you, you lead them.
Your voice: make sure its never slow-paced and make sure you speak fluently.
Talk! Don't be afraid of a person thinking of you as overly-talkative, as long as you make sure the person CAN respond you're not overly-talkative. Listen, talk, listen, talk. If the other person doesen't talk, maybe he's shy, talk more if he keeps on not talking then don't talk anymore. Anyways people prefer overly-talkative people to reserved ones that's for sure!
obviously your clothes symbolise what kind of person you are (not saying you should wear a tux to everywhere!! but avoid clothes that are specific to a genre of people (goth, jock etc)
another thing: Influence people don't let them influence you, When someone says something and everyone agrees with them, Oppose it! (if you don't believe in it and are agreeing with it because everyone else is)
DON'T ever turn the other cheek when you walk by someone who you haven't talked to in a while. If you talked to someone for at least ONE time, they've become a part of your life don't ignore them even if they ignore you. If they do that's their problem, always greet them or at least smile at them.
wow....I don't know where all these ideas are coming from, I usually take these things forgranted and these are subconscious traits I have but now I've suddenly become aware of them lol...strange.
Hope this helps.