This is an interesting question to me because I stand almost on the opposite side; today I have been mentally bemoaning the fact that there is no person I work with whom I can really be 100% truly honest with my opinions about other coworkers with (because, such talk is gossip; and there isn't a single coworker I both trust to keep my words private/to themselves, and from whom I think I'd get a sympathetic ear).

I have an anti-gossip reputation because of some crap that went down a year or so ago at work. I think that is a better reputation to have. Someone came to me and divulged gossip which I felt was way over the line and was about a coworker whom i'm quite fond of. My solution at that time was to go to that coworker and let her know. That set the ball in motion.

if I were you, first, I'd refrain. It's very hard to refrain from all gossip and honestly, as a human, I think it's unreasonable to think that we would stop talking about the other humans around us...so a better and more realistic step 1(a) - I would recommend, stop using names. Just stop. You can imply or let others pick up on who you are talking about, but stop naming people specifically. The furthest I feel comfortable going is often, "A certain manager..." or "a certain coworker." Even if it is probably COMPLETELY obvious to my immediate coworkers who I am talking about (assuming they know who I work with on what, which they should) -- I feel that 'discretion' not only gives you a cushion to fall back on if gossip comes back to bite you in the ass...but also prevents the gossip from becoming too personal or starting a bitch circle about a single person or manager. It prevents the gossip from going too far (in a single moment/conversation). It also gives the rest of your people you're talking with the opportunity to pretend they don't know who you're talking about if they don't want to engage. Or if they think what you're saying is something they are better off not knowing. (These factors are more relevant in a more discrete workplace, as mine is and it sounds like yours is not.)

The first step with this problem really has to start with you.

If someone tells you gossip which you think is over the line or harmful or untrue, you could try asking, "Should you be telling me that?"

When it comes to gossip about changes in company direction and/or expectations...I think that's a little more normal and you can't expect to stamp that out. When there is uncertainty with the company, there will always be more.

If you are a person whom others look to for advice, or confidence, and you hear gossip about the state of the company that you think is overly negative or needlessly worrisome, stand up straight, say "i'm sure it's not as bad as we think it is," and turn back to your desk and work.

Be a good example.