TheEvil
Explorer
ThirdWizard said:"Scouting" in D&D is spelled divination. Clairvoyance and clairaudience as well as scrying are the usual methods. You can fall back on things like augury, divination, or locate object or creature aslo.
If you're really desperate, you can cast fly, invisibility, and silence on someone with a good spot skill and send them into the air to look around. This is usually only useful if what you're looking for is either really big or really obvious, though, in my experience.
Arcane Eye is also an excellent spell to add to that list, though a spell caster without a high spot will miss things.