Note: the example I’m giving is D&D focussed, but the question is system-agnostic.
We’re in the early days of a new D&D group. If it keeps running, I’m planning to transition the players into Storm King’s Thunder once they reach 5th level. Storm King’s Thunder is an adventure that features a lot of giants.
I allowed the party to defer some character creation choices so we could get playing faster, and one of them has an unused language slot. The party also has a Ranger and the revised version of the class can, at higher levels, choose an epic foe against whom they get combat bonuses.
It would be very sensible if that unused language could turn out to be giantish and that the ranger could take giants as their epic foe. It would also be nice if I didn’t have to lay out to the players that there are giants in store later – they’re all new, and they won’t guess.
Are there any good story-driven ways that a GM can help "guide" players toward making character creation choices that fit the planned campaign?