Here are some unwritten rules for the wiki. I didn't know about these rules until I inadvertently broke them, so I decided to write them down for the benefit of others. Some of these are alluded to in the Guidelines, but not expressly written out.
Rule #1: Avoid adding categories to redirects.
Rule #2: When adding images to a gallery, please take care to slot them in the right places. Don't just add them to the end of the gallery.
Rule #3: Avoid creating pages with "available tomorrow" or "coming soon" or any other news-like description.
Rule #4: Do not create empty articles.
Rule #5: Avoid posting low quality images. A good rule of thumb is to use PNG rather than JPG format for the images.
Rule #6: Don't create a Transcript page or gallery earlier than midnight, Pacific time on the Friday before the new episode airs.
Rule #7: Don't create a page for a new character until the episode has aired and a discussion has taken place to see whether the new character warrants its own page.
Rule #8: Don't add captions to images that use objectionable language. This includes things like allusions to sexual conduct and acronyms that contain harsh language.
I will add more rules as I learn about them.