Observe closely as I set out to do the impossible: teach you to develop charisma, in less than three minutes.
Charisma is like the secret elixir that few understand. Here's the definition that comes up on Google:
  1. compelling attractiveness or charm that can inspire devotion in others.
  2. a divinely conferred power or talent.
Number two implies that charisma comes from God and that mere human beings can't develop it. I disagree. Not with God, but with whoever wrote that definition.
(Lean closer.)

If you want to be more charismatic, be more playful.
In almost every situation I can imagine - short of an all-out crisis - a bit of playfulness makes a person more charismatic.
James Bond has a license to kill, but makes jokes in between moments of danger.
George Clooney and Angelina Jolie both have the ability to switch from smooth and serious to playful.

The most charismatic world leaders know how to switch from somber to silly, and then back to somber. I just Googled Pope Francis, and found a photo of him with a baby goat on his shoulders.
Playfulness proves you are a real human being. It provides you with an opportunity to spontaneously connect with others, rather than to always say and do the right thing. 
I've seen countless people who are very smart, very hard-working, very adept socially... but who lack any charisma. Why? Because they don't have a sense of playfulness.
We like people who don't take themselves too seriously. Einstein may have been the smartest man of his time, but in one of the most famous photos of him, he is sticking out his tongue at the camera.
If you decide to test my advice, take it slowly. Don't buy a book of one-liners and start cracking jokes. 
Just ease up a bit. Open yourself up to possibilities, be a bit spontaneous when circumstances allow it, and every now and then... surprise the people around you.
It's okay to take your job seriously, just don't take yourself too seriously.
Bruce Kasanoff is a ghostwriter for entrepreneurs. Learn more at Kasanoff.com. He is the author of How to Self-Promote without Being a Jerk.