On Christianity Haven, we give 2 Informal PMs before giving out an official Warning. After that is a Final Warning and then a Permanent Ban. I am very lenient though and wish to not go the ban route if possible, although suspensions will happen to give members time to reflect on their behavior.
A good moderation policy does two thing - shows active members grace and allows you to coach them into better behavior, and allows you to quickly get rid of people who are harming your members. The best way to do that is allow anyone two reminders before a final warning/any ban is taken, but anything that harms someone (hacking, scamming, racism, aggressive trolling) jumps right to a final warning and a temporary ban. This protects your community, while also not being unfair to anyone who is a member of your community.
Inappropriate material gets removed and the member gets an explanation via pm. That's it. The last time I had to ban someone on any of the forums I still own was 2011.
Interestingly, other forums where I have admin that operate penalty systems for transgressions have rather high ban rates. They also have equally high numbers of members leaving after a temper tantrum worthy of a five year old.
The one moderation guidelines I wrote for Bizdustry maybe 2 years ago (can't remember exactly when it was posted), I mentioned in it what I generally believe needs to be done in most cases, if what someone did wasn't severe enough to warrant even a temporary ban. Which, was to determine if the item is minor, figure out if it is a one off event, and determine the frequency if it wasn't a one off event. If it was something that could be worked with and have leniency, I wrote that a reminder and some guidance on what to do in the future should be the preferred action. If someone were to just go out and do something blatantly wrong, then a warning should be the action, unless it was so bad that it needed the ban.
Personally, I believe that one friendly reminder is more than enough. The forum rules and terms of usage is already there for all members to get familiar with. After one friendly reminder and you keep messing up, an official warning is coming for the user.
