3 step prevention. 1. Always convey your own opinions to the people they are about. Even negative thoughts are better accepted if they come without intermediaries.
2. Use the good bad good rule for negative critique; find a quality than say your critique, and finish with a quality. e.g. "I know you try hard and do your best, but that last report wasn't put together as well as it could have been, but hey, I love what you said about production Improvement".
It is always easier to correct or give critique if the other person knows you are as observant of their qualities as you are of their mistakes.
3. Even if a person is wrong, never accept negative observations from others; ask questions like: "have you spoken him about this"? And if it isore malicious, inform the person: "John is a colleague, I don't believe this conversation will make our work any better".
If you show that you are solid, and loyal to people you have to relate too, you will not be likely to get caught into work place rivalry.
Another philosophical rule to hold onto is, "if people know your intention to respect and care for them, they will be more open and understanding with your intention to criticize". Constructive criticism is important in any healthy social environment.
Be careful who you divulge that gossip or hearsay to. If you want to confirm it, find a peer or colleague who you feel comfortable with and maybe a manager above you to gain clarification with, should the supposed info be worth the added effort.
I think the best thing to do is to just ignore it as much as possible and not participate in it. Gossip and hearsay will always be in play, participating in it will only fuel the fire. If you feel the gossip is harmful to someone then I would say something and set the story straight, but, if it's just silly gossip then I would try your best just to ignore it.
I usually ask the people participating, "if you are willing to speak in this manner about this person to each other, imagine what you must be willing to say about each other when not your not present?" That ALWAYS shuts them up! :)
Remember if they are talking about someone else, sooner or later they will be talking about you. Don't get involved with their gossip, just change the subject, and kindly explain that you don't want to be involved and then walk away.
I work in a situation like that and am very close to going to my superior and telling him that I, and many other's find it disruptive to the work environment. It need's to stop, they can go somewhere else after work to gossip! Also I just got a new i-pod!