What is a spoiler?
Spoilers are messages which, unintentionally in most cases, give the solution to a mystery, or otherwise “spoil” the story for another reader. Standard practice regarding potential spoilers is to include a spoiler warning and space both before and after the potential spoiler. If you aren’t sure it is a spoiler, use a spoiler warning anyway. It is better to be too careful than to unintentionally ruin someone’s reading enjoyment.
When someone tells you how a movie you haven’t seen before is going to end, he has “spoiled” it for you; your ability to enjoy a good surprise has been severely impaired. The same idea works in the gaming world. If you wish to post any details about any TSR products, please include the word SPOILER in the subject, and leave a full page of blank space, either by inserting a form feed character or by hitting Return about 20 times. This is especially appropriate for descriptions of modules (“We just finished S4; had a dickins of a time opening those pesky doors, but here’s how we did it…”), because there will always be people on Usenet who have not played that module, or who are currently running through that module. Most DM’s do not enjoy it when someone else gives their groups all the details of their next few adventures. So no matter how old a module is, always include spoiler warnings if you are divulging any vital details.
A spoiler is understood to be a comment or piece of information which reveals an important plot detail (for example the ending or a major plot twist), thereby ‘spoiling’ the viewer of the enjoyment of the film. It is Very Bad Form to reveal spoilers (for instance in a review, synopsis, or user collection) without flagging it clearly to allow readers to avert their eyes.