Ahh yes, the semi-random spot/listen checks.

The occasional fake Will or Fortitude save called for.

The right mix of illusions and not-illusions.

I once had a dwarf player charge headlong down a corridor to prove it was an illusion.

Boots of S&S ... 4x run. 120 ft/round face first into a stone wall covered by illusion of empty space.

I assessed the poor blighter a goodly number of d6s of damage. As I recall he dropped to -9 on the spot.