How do paranoid wizards stay informed?

[Renen]

I know it's assumed that high level wizards divine the future few days in advance, and thus enjoy a longer life expectancy. But what spells do they use specifically?

[AvatarVecna]

Legend Lore, Visions, Locate Object, Foresight, Greater Scrying, Detect Magic, and Greater Prying Eyes are all Core, and are all very useful. It's generally easier to defend yourself from divinations than to penetrate such defenses, but that's true of most everything a caster can do.

As a high TO example, Khepri has an overwhelming offense, but her defense is literally impregnable unless you cheat with Pun-Pun, the Lady of Pain, or a transcendental level deity.

[ryu]

Also contact other plane is useful. How immediately useful depends on whether you're allowed to take 10 on the check involved, and whether the spell is ruled to be able to bypass vecna blooded. Still pretty useful even if those aren't ruled in the spell's favor, but absolutely gods damned necessary is they are.