Premonitions come in all shapes and sizes. You can have a sudden hunch, a rising uneasiness, or something as startling as a vision or a voice in your head. They can warn you away from danger or tease you with a glimpse of tomorrow’s hairstyle.

Here are five common markers for a waking premonition that can help you recognize one of your own. These markers come from the interviews I did for my book, and from stories gathered over the past century.

1. SUDDEN APPEARANCE Waking premonitions come suddenly, from out of the blue, with no connection to anything we had been thinking a moment earlier. It yanks us out of our usual train of thought ad into something completely different.

2. CERTAINTY waking premonitions carry a certainty that goes beyond good sense. Whatever it is that we know or feel, we feel sure about it, even more sure than our own rational assessment of the situation. We just know. It feels important, clear, and urges us to pay attention.

3. CONFUSION When we can’t shake the certainty and can’t trace the thought back to a source we often feel confused. How did I know that? Why am I feeling so anxious about nothing? Most of us will try to scold ourselves back to rational thinking, until the future event happens and connects with our concern.

4. VAGUENESS Waking premonitions are maddeningly vague. We feel anxious but don’t know what about. We see a vision of an event but who knows where or when or how it will happen? For all the certainty we seldom have enough details to understand what is coming.

5. PHYSICAL MARKERS we might get chills, a tingling down the arms and back of the neck. We might have a clawing at the pit of our stomach. We might feel hot and bothered, restless and full of unnecessary adrenaline as our body gets ready for something we haven’t yet tracked.

6. PERSONAL MARKERS Over time we can build our own personal list of markers that tell us which images and feelings to watch and which we can push aside. For one person a dream of flowers might mean a funeral, but for most people a dream of flowers just mean flowers.