Article for Horoscope.com, created as a work for hire, 2011. Used by permission.
Halloween (a.k.a. All Hallows Eve) originated in the British Isles. On the night before the Christian All Saints Day, which coincided with Samhain, the ancient Celtic New Year's Eve, evil spirits popped in to say "boo" for one last night of revelry, and people needed protection from supernatural mischief. They might wear furs and masks so they'd be mistaken for animals and avoid having their bodies possessed. Costumed children and beggars would "go round the houses" singing and saying prayers for the dead, sometimes collecting cakes and coins -- trick-or-treat!
The animal world was evidently a buffer against the spirit world, so burying animal bones or a picture of an animal near a doorway kept ghosts from entering the house. If a bat flew inside, ghosts were obviously present to let it in. Owls were okay with ghosts, so any place with owls must be haunted. Worse, owls swooped down to eat the souls of dying people. The dead watched their loved ones through spiders; and snails entrapped overnight on Halloween could spell out your true love's initial in a romantic slime trail. But black cats remain among the most enduring omens, since witches used them as familiars. They signified bad luck (or in some places good luck) if they crossed your path, howled outside the window, or turned their back on you. Killing one on Halloween brought seven years' bad luck (although any murdering of cats strongly suggests that you are evil).
Fire, humanity's brilliant discovery for keeping away the darkness, is also a prominent Halloween symbol. A candle flame that blows out during a ceremony, or one that turns blue, signals the presence of a ghost. People had special Halloween candles that were unlucky to use at other times of year, lit by torches from a ritual bonfire after all other flames in town had been extinguished. Gazing into that candle flame could reveal the future, and any disturbance of the bonfire stones predicted that, within a year, death would visit whichever household had laid that stone. Meanwhile, the friendly Jack-o'-lantern comes from the complicated tale of a rascal named Jack who tricked the Devil and was repaid with an ember of hellfire contained in a turnip. But when that custom reached America, pumpkins were plenty and easier to carve than turnips... so that's how we know Jack!
Here's a handy list of Halloween safety tips. Dine in silence; dinner conversation may invite ghosts to the table. When walking in the dark, carry one lump of bread in your pocket as an offering to ghosts, and keep another one sprinkled with salt to ward off witches. Don't lose that bread when you turn those pockets inside out while passing a graveyard or hearing an owl hoot. Ringing a bell or leaving a turnip on your gatepost keeps the ghosts away, but don't be hurting any ghosts. That means no door slamming or hunting trips -- and hide all the knives! Should you encounter a ghost, walk around it nine times and it'll disappear. Don't wear your clothes inside out and walk backwards unless you want to meet a witch. Witches don't like horses (they prefer brooms, right?), so keep them out of your house with a horseshoe over the door. For extra protection, sprinkle salt and oatmeal on your children's heads so witches won't steal them. And don't forget the fairies. The best way to prevent being jacked by fairies is to avoid sitting under hawthorn trees, where their magic is strong.
Tying a knot in a handkerchief wards off evil, and since the Devil was a nut-gatherer, make your magic charms out of nuts. If you bob for apples, the first person to bite one will be the first to marry. If you peel an apple from the bottom, the one with the longest unbroken peel will have the longest life.