Nice post on running intelligent foes at The Monsters Know:
Intelligent Enemy Tactics
It's not really new advice, if you've been around gaming as long as I have. But it's a good, readable, and linkable source for it.
One idea I've toyed with for intelligent foes is to allow them a chance to retroactively plan for PC approaches. The GM can roll, say, an IQ roll with a cascading penalty for repeated attempts (-4 is probably workable). If successful, the monster did have something useful planned to forestall that PC tactic. A failure means exactly that - it wasn't ready.
Alternatively, make it a "Gizmo" - 5 points per use for "Tactical Gambit." Each use allows some retroactive planning using the creature's intelligence and native abilities to be ready for a situation it could have reasonably planned for had the GM thought of it ahead of time.
This can be a good way to do unplanned encounters with intelligent foes that would reasonably have planned. Because GMs don't always want to just wing it when the PCs veer left and end up in some area or situation the GM just didn't have time to plan for.