"I think the scariest person in the world is the person with no sense of humor." - Michael J. Fox
For me it's effortless. I can get strange women smiling at me and talking to me on the street and in stores. Often, laughing. On the other hand, people with no sense of humor can't stand me. They're rare, fortunately.
I tell people I've been this way since I was 12.
But perhaps I wasn't born with it. I do know it's an art, and if you study it a bit, a science. For example, humor is when you take two unrelated things and find a connection between them. That's the Aha! moment. (I once saw an electrician standing on a ladder with his upper half in the ceiling. I told the people I was with, "Poor guy...he's half the man he used to be." Everyone groaned.)
I also know all humor is based on some degree of hostility (except puns) because there are winners and losers. Satire? Based on trying to correct human imperfections. General humor? Acceptance of what we are, with no attempt at correction. Irony? Saying one thing and meaning the exact opposite.
Jean Shepherd, for example (who writings were the basis for A Christmas Story) was about Acceptance of our situation. And this scene is about Acceptance:
I was raised in a large extended family on the father's side. He had five siblings and they had all their husbands and wives and kids. I was the favorite of some of them and they encouraged me to be funny at family gatherings.
A lot of kids are funny but are not encouraged by their families. And with families breaking up or not forming, how many extended families are left? (By the way, a noticeable number of boys I know raised by single mothers don't have a sense of humor.)
(Incidentally, my paternal grandfather taught me how to make a noose, which the only complicated knot I know how to tie. He also took me "hunting," which was about his retarded beagle chasing imaginary rabbits.)
I was also a class clown and that was not encouraged. I got in trouble and had to write sentences on the blackboard, like Bart Simpson.
I also have a sister 13 months younger than me and when her friends came over I would torment them. They thought I was funny to this day and still bring up how I acted then.
You could say I had a lot of practice. And after a lot of practice it becomes natural.
I once read an article about improvisational comedy. The only rule is "Never refuse an offer." When one person says something, build on it. Which is why when I get together with friends what we come up with is hysterical.
My extended family never refused my offers and instead built on them. School refused them.
I've met some people who apparently have no sense of humor. How this happened I don't know, but I suspect they didn't have extended families or parents who didn't encouraged them. And as for being encouraged in school, forget that.
I tell people, "I am not only witty; I am a cause of wit in others."