- Do not ever conceal the name of the trope in a list of trope examples, the list on the work's page.
- Do not ever conceal the name of the work in a list of works using a trope, the list on the trope's page.
- No spoilers in the main body of the description, above the "Examples" line. Just don't do it.
Okay, that's the policy part. Now we can talk about something that bugs tropers who have an interest in making things look good: Swiss-cheese entries, entries where single words and short phrases are cut out and other text is left visible. Face it, it looks like crap to people who have the spoiler font blanking effect turned on, which is the vast majority of the readers. It is the default. Having specific rules about what to hide in the example is too complicated. It boils down to: Think about it. Think about the casual reader, who doesn't care about spoilers. We know it seems important to fans of a given work, but the far and away majority of readers are not people with a fannish mindset at all. We who edit are mostly fannish, but the people who edit are less than 1% of the people who read the wiki. Let's continue to write for the casual reader. It is our best way to convert them to fans. Finally, avoid Wicks and Potholes in spoiler tags, because mousing over them reveals what's beneath, making it pointless to conceal them. Plus, they stand out in some browsers.
There are some special-case rules for not using spoilers in the Spoilers Off page. But, please, if you don't see your specific case listed there just use your head and favor the needs of the casual reader.