Facebook pages and LinkedIn groups offer some great tools for nonprofit groups that want to encourage discussions about their causes.

An environmental charity, for example, can create a Facebook page to point to news about the latest research, to start discussions about their work, and to create connections for people who are interested in finding others who care about conservation.

Unfortunately, these mini-networks can quickly devolve into grab bags of unrelated information and spam.

Not everyone who signs up to participate on a Facebook page or LinkedIn group joins for the same reason. Some people join to promote their own agendas, to advertise their own products or services, or simply to be trolls.

If you truly want to keep your group on target and to keep your members engaged, it’s important to take steps to keep out the people who aren’t interested in substantive discussions.

And to do that, it pays to be direct.

This has been my approach with The Chronicle of Philanthropy’s group page on LinkedIn, which attracts its fair share of members who want to use the group as a promotional vehicle, rather than as a place to hold conversations about the nonprofit world.

To combat that problem, I’m diligent about deleting posts that are promotional or off topic. In some rare cases, I’ve kicked people out of the group.

And I’m careful to make sure that I post occasional reminders to members about the rules of engagement. That way, there is no confusion about what we’re trying to accomplish with the group.

Here’s what I wrote in a recent reminder:

“If you’re posting announcements about upcoming charitable events, your consulting firm’s Web site, or another clearly promotional item, please note that you run the risk of having it get deleted.

“The etiquette for this group is pretty straightforward. This is a place where we hold discussions about topics of interest to those who work in the broader field of philanthropy. It’s designed to help people get new ideas, debate topics, and find resources that will help them advance their careers or do better work.

“It is not a place to promote events, products, services, or the like.

“We’ve been able to keep this group vibrant by preventing it from becoming a dumping ground for spam and promotion. Please don’t be offended if I delete your post. Just know that I’m working to keep it as a vibrant forum for our readers. “

I’ve found that such messages cut down on the amount of off-topic messages that are posted to the group.

And they build goodwill among group members who are there for the right reasons.

As one Chronicle group member wrote: “In many so-called philanthropy and grant makers’ communities at LinkedIn, I felt drowned because the issue of how to make fundamental changes got lost in masses of professional advisers who used the discussion for advertising their service over and over again to get clients. I entered a dozen of so groups and got bored and went away again. I just was about to leave this group too. Then your ‘gentle reminder about the rules of this group’ popped up and I thought ‘hey’ the owner cares. It’s not the mass of started discussions that make a good group. It’s the quality of the discussion.”

How do you set the rules of discussion for your Facebook and LinkedIn communities? Post a comment to share what has worked best for you—and what has failed.