A spoiler should be considered any piece of information that isn't yet known by the general population. Speculation is fine, and vague references are ok, too. Just make sure they stay vague enough.
1. Posting spoilers
All spoilers must be either :
- posted in a spoiler-friendly forum;
- posted in a thread with a fair warning in the title ("*spoilers*" will do);
- enclosed in spoiler tags like so: [spoiler]spoil spoil![/spoiler].
If you do not respect this, you will be asked to remove the spoilers.
2. Avatars and signature pictures
Only pictures that do not reveal plot points (character deaths, duels, etc.) are allowed. If there is text in the pictures, it should not contain spoilers either.
If you still want to use a signature that contains spoilers, either use the [spoiler] tags if it's text or a link with an apropriate warning if it's an image.
3. Be courteous