I don't have much to say about Hallowe'en, except:
1. There's an apostrophe in it. It's an abbreviation of "All Hallow's Eve."
2. It falls around the same time (occasionally the same day) as the Gaelic harvest festival Samhain, and therefore should be celebrated as religious observance by neo-pagans.
3. It precedes the important Christian festival of All Souls' Day, in which the faithful dead and canonised are remembered and (in Catholic tradition) prayed for and to (in the case of the saints). I may say a prayer at midnight, if I am awake then.
4. Conversely, anti-theists who proclaim that any belief in a religion is wrong should have no part in Hallowe'en, and should not acknowledge its existence!
5. The month of October is not Hallowe'en. October 31 is Hallowe'en. If you must celebrate, at least do it as close to the date as you can get. I'm specifically talking to you, children playing trick-or-treat three weeks ago in the town centre.
6. Trick-or-treat is not an acceptable way to celebrate this festival. It's a commercial custom mostly stemming from the USA, and is in fact disrespectful to all to have a right to celebrate this day.
7. There's nothing in the original doctrine that refers to ghosts, spirits or especially devils, demons or witches. The faithful departed are in Heaven and therefore wouldn't be ghosts. Modern witches who celebrate Samhain should not be depicted as having green skin, long black hair and flying on Nimbus Two Thousands.
8. Something to do with sex should go here, but I can't think of anything offhand.
And two bonus geek facts...
9. Cliff Barry, who played the villain Lissard in Knightmare, married his wife Juliet on Hallowe'en. His best man was Mark Knight, who also played a villain - Lissard's master, Lord Fear!
10. The final Knightmare book, Lord Fear's Domain, is set on Hallowe'en.
TL;DR? Short version: Have fun on this day, as you would on any other day. Just don't be an idiot.