I am part of a Facebook group for community professionals and yesterday there was a thread sharing examples of general community guidelines. I've compiled a list of what I consider the best of them (across a broad range of community types), so with any luck you'll find them useful.
Here are the guidelines (and the discussion around them) that I wrote for this community (when we move to Discourse).
Hotcouponworld have gone for nice and simple
rheumatoidarthritis.com (appropriately) takes a more serious approach
Becca McArthur drew from Wikipedia, StackExchange and DIY to write these for Socratic
Here is an example from a gaming community