You MUST use original material. The audience will forgive you ANYTHING but being boring. If someone else has already said it, say it in a completely different way. If it's a cliché, throw it out! 

Sol Stein's advice in DIALOGUE FOR WRITERS is equally useful for speakers: "The majority of novels are turned down, even those written by well-educated people, because they are cliché-ridden. And so is a lot of popular fiction that does get published." 

He says, "A cliché is a hackneyed phrase -- stale, trite, banal, commonplace, corny, dull, musty, redundant, repetitious, tedious, threadbare, timeworn, tired, tiresome, worn-out, boring. If you prefer to focus on just one definition, it should be 'tired from over use.' Clichés weaken your message, having little or no effect on the reader. 

"Words have power. Words strung together in clichés have lost some or all of their power. Clichés are a sign of a tired mind that settles for a well-worn rut instead of climbing to exciting new heights. Your job as a writer is to energize people, not put them to sleep." 

When I was conducting a two-day speaking school in Los Angeles, a handsome, well-spoken student gave an eloquent talk -- but it was all rehashes of material from motivational books he had read. Everyone had heard the messages before, over and over. No one felt any connection to the student. Everyone was bored, yet he had lived a fascinating life that his audience wanted to hear about. So I asked him to describe his life, starting at the beginning. I call this the "once upon a time" technique. As he spoke, he became excited, and his audience did too. Within his reminiscences was fresh, stimulating original material that could become the core of his message.