I don’t have actual scholarly statistics to back this up, but I wouldn’t be surprised if good luck charms weren’t one of the most common — maybe the most common — concepts in folk magic.
After all, they’re alive and well today, even when many other types of folk magic have become far less widespread. Do you have a lucky pebble in your purse, a lucky tie you wear to all your job interviews? Even when we know these things have no actual power, we often still make use of them, tongue only partly in cheek. It’s pretty basic psychology: if a given object is associated in your mind with one or more occasions when good things happened to you, then it’s reassuring to have it on hand when you want things to go well again. I have a five-yen coin in my purse that I found when scouring the ground in Okinawa for my lost wedding ring three years ago; five- (and fifty-) yen coins are supposed to be lucky because of the holes in them, just as stones with holes with them are often reputed to be special, and hey, I found my ring not long after that. Maybe the charm’s only effect is to soothe your anxieties a little bit when you’re going into a stressful situation . . . but that’s still a useful effect, and may cause things to turn out better as a result.
Pretty much anything can be a good luck charm. Some of them are codified; crosses, saints’ medallions, holy relics, and other such religious objects often have that association in addition to their religious function. In the Middle East and North Africa, the hamsa or Hand of Fatima, a hand-shaped symbol, is a defense against the misfortune brought by the evil eye; the nazar serves a similar purpose through a similar geographic region. Male Roman children were given a bulla, female children a lunula — two kinds of protective amulets, needed because children are often seen as being especially vulnerable to malicious forces. In East Asia, the creatures variously known as shisa (Okinawa), komainu (Japan), or shi (China) are protective symbols, warding off evil spirits from important locations like temples. At Japanese temples you can also buy omamori, small amulets that bring good fortune, often for specific purposes like upcoming exams or travel safety.
But as my coin example shows, it can also just be a random item you associate with good luck, because it’s pretty or something good happened to you in a related context or just, I dunno, everybody agrees that’s how they work. Stones seem to be common for this, as are coins — especially, as mentioned above, if they have holes in them — but not all good luck charms are durable; four-leaf clovers are perishable but very well-known. Rabbit’s feet are one of those things I took for granted until I stopped to think about it, at which point it started to seem a little gruesome. (I’m pretty sure most of the rabbit’s feet you see sold in gas stations and the like are not made from real animal parts, though.) Horseshoes, mentioned in my previous essay, may derive some of their reputation from the iron they’re made of, which in the British Isles was reputed to ward off faeries and their mischief — not to mention that blacksmiths have often been seen as having magical power.
Good luck charms are also behavioral. Have you ever knocked on or touched wood after speaking of your good fortune or the possibility of bad luck? The idea is that you’re calling on the spirit of the tree to make sure malicious forces don’t notice what you just said and decide to screw you over. Crossing oneself, spitting, turning around three times — there are all kinds of ritualized behaviors people may call on, whether they’re codified in the culture or just personal superstitions. (Taken too far, some of those things are manifestations of obsessive-compulsive disorder.) Blessings are a major category here, with various prayers and invocations asking the gods or their intermediaries to gift the target with good fortune.
My common refrain in these essays is, “I don’t see this very often in fiction.” Occasionally there will be a passing reference to a character “making a sign to ward off the evil eye,” but we rarely get a description of what that sign is — maybe because gestures often take more words to describe than they’re really worth. But if you put the first usage of it in a context where taking that time to describe it won’t disrupt the flow of the narrative, and if you give it a name (like we might say “the sign of the cross” or “the fig sign”), then you can use it repeatedly later in the story and your reader will have a better sense of what it means. You can mention children wearing or receiving or losing their protective amulets, or your protagonist reaching into their pocket to touch a well-worn bit of stone, or streetside kiosks selling good luck charms of all kinds. This kind of thing might be less common in science fiction, because so much of that genre takes for granted the idea that people in the future will be less superstitious than they are today . . . but of course that won’t necessarily be the case. And in fantasy worlds, you’d expect to see this kind of thing all the time, especially when society at large knows that supernatural forces have very palpable power to affect the world around them.
Any lucky charms in your life, whether they’re little ritualized habits or objects you associate with good fortune? Do you know where they come from and why they carry that association?