You don’t always need to start with a joke. After all, you are probably not a professional comedian, and no one expects you to be. And starting a speech with an irrelevant joke, no matter how funny it is, like “Two men and a dog walk into a bar…” is almost guaranteed to make you look like a fool.
But if your natural sense of humor wants to come through, let it. Especially if the joke applies to you or to your immediate surroundings, and especially if you are making fun of yourself, like Guy Kawasaki is here.