
You've got two options for this, the way I see it.
Option one is to do the whole thing narratively. Talk to the person OOCly and determine what they want their character to hear, and what you might be able to divine with your powers (or lack thereof). Then, you can RP out the scene. A less scripted approach to this is to mention OOCly that your character is a seer, and if they want to toss anything your way that they could suddenly "see," you'd be happy to incorporate that into your RP. With both of these approaches, the ball's in the other player's court (thereby avoiding any godmoding or powerposing) and the entire process is built around supporting the narrative.
Option two is to do a cold reading. It takes some practice, but it's a classic mentalist trick. Wikipedia article and Skeptic's Dictionary article can get you started. There's also some videos from conjurers showing how it's done, and James Randi has several appearances in various media that demonstrate it. (If you want to see it done poorly, just watch Sylvia Browne or John Edwards. If you want to see it hilariously explained, watch the South Park episode, "The Biggest Douche in the Universe," S6:15.) This approach will let you give a convincing reading that's dynamic for the other player, but it doesn't necessarily serve any larger narrative goals.
As a side note, I'm not looking to get into an argument about the reality of seers, psychics, or fortune telling in real life.
I'm just trying to cover the ways that you can portray them in RP.
EDIT: Lorewise, I'm not personally aware of any NPCs with precognition, but that doesn't mean they don't exist.
Option one is to do the whole thing narratively. Talk to the person OOCly and determine what they want their character to hear, and what you might be able to divine with your powers (or lack thereof). Then, you can RP out the scene. A less scripted approach to this is to mention OOCly that your character is a seer, and if they want to toss anything your way that they could suddenly "see," you'd be happy to incorporate that into your RP. With both of these approaches, the ball's in the other player's court (thereby avoiding any godmoding or powerposing) and the entire process is built around supporting the narrative.
Option two is to do a cold reading. It takes some practice, but it's a classic mentalist trick. Wikipedia article and Skeptic's Dictionary article can get you started. There's also some videos from conjurers showing how it's done, and James Randi has several appearances in various media that demonstrate it. (If you want to see it done poorly, just watch Sylvia Browne or John Edwards. If you want to see it hilariously explained, watch the South Park episode, "The Biggest Douche in the Universe," S6:15.) This approach will let you give a convincing reading that's dynamic for the other player, but it doesn't necessarily serve any larger narrative goals.
As a side note, I'm not looking to get into an argument about the reality of seers, psychics, or fortune telling in real life.

EDIT: Lorewise, I'm not personally aware of any NPCs with precognition, but that doesn't mean they don't exist.

The Freelance Wizard
Quality RP at low, low prices!
((about me | about L'yhta Mahre | L'yhta's desk | about Mysterium, the Ivory Tower: a heavy RP society of mages))
Quality RP at low, low prices!
((about me | about L'yhta Mahre | L'yhta's desk | about Mysterium, the Ivory Tower: a heavy RP society of mages))