Aside from MMOs, which are predictable to a fault, adventure games tend to lean heavily on surprise encounters. The player turns a corner and "Boo!" -- danger leaps out and combat begins... or a story character appears and dialog begins.
It doesn't have to be that way. An alternative is to show the player exactly where they're going, exactly what's coming, thereby building anticipation.
Think of LOTR. Frodo sees Mount Doom long before he reaches it. In fact, it's in almost constant view as he travels from location to location, inching ever closer.
Or what about when the heroes are guarding Helm's Deep. The enemy army doesn't advance on the fortress in a mad rush. They march slowly toward it. There's a lot of time for anxiety to build.
The player could be walking through a town and see an event or important character at the end of the road. It might be up to the player whether to go straight to the scenario or to meander through every building and conversation along the way.
A massive battle might loom in a valley ahead. Enemies or other content might fill the path leading down. While that content is engaged, the battle remains in sight and becomes louder with each step. As the player gets closer, new sights and sounds may appear. When the player gets close, stray arrows or bullets might land around him.
Surprises can be a lot of fun, but it can also be fun to know exactly what's coming.