“ Chekov's Spell -- This spell has a two-fold effect. The first is to make the target item almost-unnoticeable to anyone not specifically looking for it. The second is that someone who has seen the item will remember it when they encounter a situation that would be perfectly solved by use of said item.”
“ He's a non-descript man, with his pushcart. On it he sells nothing more exotic than jars of sun-dried tomatoes in oil and pickled vegetables. But he's always out there, in the courtyard of the great Guild of Wizards, in most weathers, and he'll have a kind word for you, and a jar.”
“ The PCs are walking along the road, when suddenly a bunch of bandits attacks. The player's dismiss it has just a random encounter, when they find an ornate ring on the leader, obviously out of place with the seemingly poor bandits, who could only afford cheap leather and weapons. This ring has a symbol on it, which, if researched, sets the PCs on a quest. And from then on, the players don't look at random encounters the same way...”