"Analyzing humor is like dissecting a frog.  Few people are interested and the frog dies in the process."  E. B. White

"Humor is a train wreck of the mind.  You get a train of thought going one way then wreck it."  source unknown

"Don't let a person, place, or thing go by without asking, 'Is there something funny I could say here?'"  Bill Gove 

The people who know funny laugh... humor is about making people laugh.  It's that simple and it's not easy, although it looks like it.  The basic structure of humor is:

Setup (Get them thinking):  "Some people say public speaking is the greatest fear..."

Waste (Continue the thought):  "...not quite.  Fear of spiders and death are worse..."

Punch Line (Derail it): "...my greatest fear is dying... (pause) speaking."

Important Note:  The last word of the punch line is the punch word.  "Take my wife, please." is funny.  "Please take my wife." is not... "...but it may be convenient." may be. 

Important Point:  Aspiring speakers often ask, "Do I have to be funny."  yielding this answer, "Only if you want to get paid."  Cute, but untrue; however, the best professionals engage audiences and humor can be a great connector.