Have the player roll

Use a roll to reflect uncertainty or risk, or if you want there to be multiple tiers of success. The result of the roll can dictate the results directly, as with Know Things. Or it might affect the choices that get made, like how Seek Insight's Seek Insight roll determines how many questions the player gets to ask.

"A roll" usually means that the player rolls 2d6 and adds a stat, with different results on a 10+, 7-9, and 6-. But see step 5 for other options.