The term “synchronicity”, coined by Carl Jung, is a key idea that applies across all different systems of divination. A synchronicity is a meaningful correlation between our inner thoughts and an event in the external world.
Thinking of an old song and then walking into a store where it happens to be playing.
Contemplating a change of career, then being phoned by a friend in a distant city who is starting a new company and looking for a partner.
Feeling a great need for peace, then having a dove settle onto the fence in front of your house.
Synchronicities are different from coincidences because (1) they connect the inner and outer worlds, and (2) we find them meaningful, full of significance. Two external events that happen at the same time, no matter how unlikely they may be, are just a coincidence, not a synchronicity. (For example, if two people both get flat tires on their cars on the same day.)
Most divination techniques might be thought of as ways to encourage synchronicity to happen. If you draw a tarot card while thinking about an important question, for example, you are setting up the possibility of a meaningful correlation between your question and the card. Since the tarot symbols are designed to be provocative, stimulating, and meaningful, they lend themselves readily to this kind of thing.
But as ancient people knew very well, unplanned external events can also convey meaning, to those who are open to finding it. Once our minds become accustomed to seeing things symbolically, then the whole world becomes a treasure trove of potential meaning.
One of the most basic forms of divination, therefore, is simply being open to synchronicity and noting any events that speak meaningfully to you about the matter on your mind. No special tools are required, although a notebook might be helpful. This is a kind of divination you can do for yourself, anywhere, any time!