If you're speaking at some sort of formal event, you had better leave the casual jokes at home. Likewise, if you're speaking to people who aren't expecting you to be a world leader, then it's best not to approach the situation like you're about to address the United Nations.
Think about the point you're trying to get across and the concerns of the people you're trying to convey the message to. But be yourself. You don't want it to sound contrived. Just be considerate.