Gossip is negative and unproductive behavior. Healthy humans gracefully "walk away" from gossip and never pass it on. The secret is to rise above gossip by showing disinterest. Sell your company and your personal strengths rather than rumor mongering about the competition.
Some of my hostages knew it all and insisted on sharing their "knowledge," mostly when it was not requested. This aberrant behavior can be the kiss of death for a print salesperson. If salespeople dispense unneeded advice or insist on sharing irrelevant knowledge, buyers view them as boors. Nobody wants to spend much time hanging around boors.
On the other hand, if a buyer asks you a question that you can't answer, for goodness sake, say you don't know and will have to get the answer. Admitting you don't know something is integral to integrity, and we all know that honesty is the first characteristic required for print sales. Someone, many years ago, said, "If you always tell the truth, you never have to remember anything."
My print buyer and banker hostages were great gloaters. To hear them tell it, you would think they were single-handedly responsible for whatever success enjoyed by their employers. For that matter, whatever the subject, they were ALWAYS right! People hate that kind of abnormal behavior. It stinks. They were great at saying, "I told you so." I recently read the only time you should say this is when you say, "I told you that you had all the qualities for the success you have enjoyed."
Great salespeople instinctively know how to share the credit. They share it with their customers whenever possible. You might say, for example, "Your project management and responsiveness really made it possible for us to deliver this job on time. Thank you." They share credit with their co-workers by saying things like, "Our pressroom guys worked very hard to deliver what you wanted."