Perception is the psychic's main tool. Perception isn't just how we see things, but also how we make them be.
Several examples: A key is just an oddly shaped piece of metal unless you know it can be used to open a lock. Fruit becomes food after you realize it's edible. Color isn't color until the brain makes it be.
You don't really know a thing until you know all its relations to everything else - and many of these relations can be decided by you, effectively creating the reality of that thing. Psychic perception isn't just passive - psychic perception is also active.
Many of the deep layers of reality are invisible to us, hidden in plain sight. We don't see them because we don't look for them, and what we do see we dismiss because these perceptions don't fit the reality we wish to see.
A psychic does his or her best to maintain an open attitude and work on perceiving directly instead of just operating with shallow (and often incorrect) assumptions.