My
forum is relatively trouble free... now. It was not always so. I started it 15 years ago. I only have just over 20K members now.
When I first started the forum, I setup four rules, which eventually expanded to six rules.
http://www.twtex.com/index.php?page=rules
Perhaps the single biggest thing I did was to prohibit foul/vulgar language/images and to insist on civil behavior from the very beginning. At first, this made for a LOT of moderation work even when the number of users was only in the hundreds. However, over time, this has had a HUGE impact on the culture of my forum and is perhaps the single most often cited reason for why people join and stay on my forum. Let's face it, when people interact over the internet, it is hard to judge tone and sarcasm under the best of circumstances. Prohibiting the foul/vulgar language goes a LONG way toward preventing people from flying off the handle and having threads devolve into flame wars. Now, I rarely have to do any moderation on the forum beyond moving the occasional thread to a more appropriate location. With the internet being a sea of crazed angry people thrashing each other, my forum is seen by my users as a nice break from all that. I am frequently contacted by new users that specifically mention this as being a reason for them joining and even choosing to donate to help with expenses.
When I do get a new user that is unfamiliar with how users are expected to behave, the other users are pretty good about informing them in a polite way rather than slamming them. If users insist on "misbehaving" I will contact them and basically give them all the same "speech". Do you want to be known here for being a pain in the butt putz, or do you want to be known here for being someone that other users respect because of the quality of your contributions? Amazingly, this has worked quite well over the years even with some of the worst case users. In 15 years, I have only had to outright ban maybe 2-3 people. I have had a small handful of users decide my forum was not for them and they left voluntarily.
How I "come down" on someone also makes a BIG difference. No one, even when they are 100% guilty and they know it, likes to have a hammer dropped on them. So I try to engage them, like the "speech" approach I mentioned above. I try to avoid the heavy handed my way or the highway approach. However, I do let them know that ultimately, they are guests and if they cannot or will not conform to expectations, they will be removed.
ALL of my members have the ability to report a post. This creates a new thread in the Moderator forum. This is rarely done because of bad content and is more often just something along the lines of "needs to be moved to off-topic" or something similar. Only rarely does one of us have to wade into a thread and start editing/removing content. Usually, a warning will suffice to keep people on track. If that fails, we occasionally will lock a thread if it is beyond redemption by trying to clean it up. If it is really bad, the entire thread gets nuked. Again, I did more of this in the beginning, but when folks realized I was serious, most relaxed and quit causing trouble. We almost never do it now. I tell folks that I do not moderate for what they say so much as how they say it.
I have a handful of general moderators, maybe 3-4 that are active. I have two other admins that help me with stuff like moderating new accounts. These were all members with solid reputations that I knew personally and were only added after the site had been active for a few years. Prior to that, I did it all. When I started adding additional admins and moderators, I made sure they knew exactly what I expected of them and that they were familiar with my style of running the forum. We don't all see eye to eye on things like politics, but we are on the same page with regard to how such discussions should occur. I often get blamed for being a right wing nut job biased against left wingers on the same day that I get accused of being a left wing nut job biased against right wingers. So I figure we are doing it right ;-)
My biggest issue now is spammers. Before November of 2015, I got a small handful of spammers trying to create accounts every day. It was easy to manually sort them out from real accounts and delete them. Then, after November, it was like someone flipped a switch and I started getting anywhere from 200 to 500 spam accounts being created daily! Fortunately, most of them cannot answer something as simple was "what does 2 + 2 equal?" That at least lets me run a query to pull out pending accounts with anything other than 4 as the answer so I can bulk delete them. A small handful may still get through that initial filtering and I can usually catch those by checking IP addresses and looking at other fields filled out during the registration process.
I have found over the years that I have a core of users that are lifers. They are never going away short of dying. Then there are the users that show up, get real active for a time, and then just fade away. Sometimes, these users will come back after a while. They might get out of riding for a bit for any number of reasons and then get back into it later. One of the things I do that helps bring people back is to send out a mass email once or maybe twice a year. It is usually just something short, essentially a reminder that the forum is still here. That will often result in folks coming back for a time. It also serves to let me know which users have bad emails. If they have not been on the site in more than a year, I might delete the account. Otherwise, I set a notice for their account so that if they do log into the site, they are informed that they have a bad email. When I am contacted by these people when they do show up again, they usually stay because they fix the email and get notifications from the site again.
I think a BIG issue for many users in the last few years has been the rise in the use of mobile devices to access the forums rather than sitting in front of a computer. I am still running vB 3.8.1 and it is not mobile friendly. Some use Tapatalk, but neither they nor I really like it. Users often want to be able to upload images directly from their phones to the site, but I don't allow them to upload attachments bigger than 640 X 480 because I am not here to be a free image hosting site for them. I am in the process of migrating from vB to XF2. Also, I am moving from a server which I own and which is 11 trouble free years old, to a VPS setup. Hopefully that will address some of the mobile related issues.
Users need a reason to come to the site. For my forum, technical help is a big reason. Something is wrong with their motorcycle and they need to know how to fix it. Or, they want to add some farkles to the bike and want opinions on which route to go with accessories. Some also come for advice on what bike(s) to buy, to read ride reports from other riders, to learn how to plan trips, to find things to see/do in a particular region, etc,... After that, there is just the general "hanging out" aspect of being part of a community, which often takes place in the Off-Topic forum. IF the tone of the community is harsh/hostile, most folks won't come around for more than just the technical stuff. If it is really bad, they won't even come for that... This is why I placed so much emphasis early on with getting people to be civil towards each other.
One thing I did is put a password on my Off-Topic section and then made the password publicly available. It was an easy way to prevent the forum from showing up for those that did not want to see it. If they were not logged in to the OT forum, its content was essentially invisible to them. It was also a way to let people know that if they were going to visit the OT section, they needed to abide by the rules, kind of like an "I agree to the terms" check box. This made the people that had no interest in the OT section very happy as they did not have to do anything to prevent seeing the OT section or any threads therein. They always had the ability to use the ignore features, but apparently that was too much trouble...
Dang. That was a long post!