What are the unwritten rules of Halloween?

DoYouRemember.com came up with eight of them, which include:

• Don’t guess what someone’s costume is unless you KNOW what it is.  You might offend them.  So if you’re not sure, just ask…especially with kids.
• Don’t bring bloody decorations into the office.  If you decorate your desk, try to keep it fairly PG.  Not everyone likes gore.
• Don’t wear an offensive costume.  Even if it’s a joke, it’s risky. (Here’s Good Housekeeping’s list of costumes you should probably avoid.).
• Don’t be shocked when someone posts photos of your costume on Facebook…nothing is private anymore.
• DO teach your kids to be polite trick-or-treaters.  Make sure they say thank you every time even if it’s candy they don’t like.

What rules would you add?