Foiling Divinations

[ReproMan]

(My apologies if there are posts that deal with this already; I tried a search and didn't see much of anything.)

Quick question: How can a mid-level caster effectively shield himself and his posse/lair from pesky PCs armed with various Divination spells? Suggestions and advice, both magical, mechanical, and sneaky, are all appreciated.

People from 'Living and Dying', don't read too much into this; the guy has some tricks up his sleeve you ain't gonna see coming, no matter what gets suggested here.

[Mr. Friendly]

Hrrm, well there is Mind Blank, not exactly mid-level though.

Nondetection is pretty good.

[Frosty]

What about Misdirection?

[Miles Invictus]

Contamination of evidence. Steal random personal effects from random people and leave them for the PCs to find. Yeah, they'll pick up the guilty party, but they'll also get a lot of false positives.

Mage's Private Sanctum (http://www.d20srd.org/srd/spells/magesPrivateSanctum.htm) blocks many divination effects and can be made permanent. Unfortunately, that's at CL 13...not quite mid-level, but maybe your BBEG just happened to find it. They're lucky like that, or so I hear.

Hallucinatory Terrain (http://www.d20srd.org/srd/spells/hallucinatoryTerrain.htm), extended, can screw over a lot of Scrying tactics if your BBEG is frequently in natural terrain.

Amulet of Proof against Detection and Location (http://www.d20srd.org/srd/magicItems/wondrousItems.htm#amuletofProofagainstDetectionand Location). Expensive, but useful.