These brief bits of humor are quick and easy to deliver and they don't have to be all that funny to be effective. If you are a little apprehensive about using humor, this is the place to start. The audience likes one-liners, because they can get a quick mental break from content heavy material. Also, if the audience is there to get high levels of content, they don't feel you wasted their time with long stories and jokes. Most public speaking resource books are broken down into categories.
Prosperity is that period between the last installment and the next purchase.
You'll run across one-liners everywhere once you start looking. Some will even have two lines. Write them down too, and start adding them to your public speaking engagements. Behind every successful person stands a bunch of amazed co-workers. My accountant is shy and retiring.