A good ad is a marvelous, magical thing. An object of emotion as well as intellect. A work of art.

Once you've done one, you know what a good ad can do. Turn nerves taut. Make fellows mellow. Raise eyebrows or raise hopes. Inspire or intimidate or influence. Impart information that motivates action.

A great copywriter once wrote, "A good ad is like a good sermon: It not only comforts afflicted, it also inflicts comfortable."

But question of moment is this: How do you know -- before a single living colleague, client or consumer has laid eyes on it -- that you've done a good ad? That it's right time to stop all thinking, talking, writing, doodling and designing. The right time to click on "save" and call a meeting?

It ain't easy, knowing that moment. Because a good ad isn't like 99-yard run kickoff return that everybody in stadium can follow as it turns into a touchdown. Or 4th of July fireworks display that gets everyone oohing and aahing in unison.

A good ad is hard to recognize. Often because it's hiding in blah advertising meetings and windy memos. Lost in dim product descriptions and lengthy creative briefs. Or even gone missing inside another ad.

A good ad is difficult to get your hands on. Like a glob of mercury on a glass tabletop. Slippery and elusive. (On other hand, Leo Burnett said, "I have learned that any fool can write a bad ad, but it takes a real genius to keep his hands off a good one.")

It's inevitable. It will happen at work, at a party, or a job interview. Even a client meeting. If you're in marketing communications biz long enough someone, some time, somewhere is going to ask you question: "Where do you get your ideas?" The first thing to remember when this happens to you is to remain calm. Nobody who asks this question expects you to bore them to tears by actually discoursing on "creative process" (which someone once described as "making sausage and you don't want to know.") On other hand, you don't want to sound totally clueless either. So, here's what to do: Plant your feet firmly, look your questioner in eye and let one or two of following witty and wise sayings flow smoothly off your tongue. They're short and sweet -- and guaranteed to make you sound brilliant. And by way, don't feel guilty about borrowing any of them because, as Voltaire said, "Originality is nothing but judicious imitation."

"I don't know where my ideas come from...however ... one key ingredient is caffeine. I get a couple of cups of coffee into me and things just start to happen." - Gary Larson

"The best way to get a good idea is to get a lot of ideas." - Linus Pauling

"I shut my eyes in order to see." - Paul Gaugin

"Some men see things as they are and say, why. I dream things that never were and say, why not." - George Bernard Shaw

"Eighty percent of success is showing up." - Woody Allen

"An idea can turn to dust or magic, depending on talent that rubs against it." - Bill Bernbach