How did it happen in the movies?
At the end of “The Fellowship of the ring” we saw Aragorn, Legolas and Gimli starting their pursuit of the Orcs that had captured Merry and Pippin. Now we meet them again on their long run. After three days of chasing without rest, Aragorn stops to listen to the earth. He discovers that their enemies have sped up their tempo. Somewhat later they find one of the leaf-shaped brooches of the Lorien coats and start hoping that the Hobbits might still be alive…and heading for Isengard.

How did it happen in the books?
The three friends started their Orc-hunt in the early evening after Boromir’s funeral boat was made, and after one night and day of running, they find some corpses of Northern Orcs, probably killed in an internal fight. When they see the White Mountains appearing in the south, Aragorn sings a longing song about Gondor. Then they find the brooch of the Elven-cloak and Aragorn deduces from the rather small footsteps that it must have been Pippin that dropped it.
The second night, they decide to rest, for it is possible that they’d miss another sign of the hobbits –or loose the track- if they keep running in the dark, moonless night.
At dawn they know that the Orcs are even further ahead, they have not rested and are now far beyond Legolas’ keen eyes. But “Where sight fails, the earth may bring us rumour” and so Aragorn stretches himself upon the ground and listens… Far away seem the sounds of the Orc-feet, but they do not hesitate and start their next day of pursuit.
This night too, they rest, because they are tired and weary of their long run. Or as Aragorn says: “I am weary as I have seldom been before, weary as no Ranger should be with a clear trail to follow. There is some will that lends speed to our foes and sets an unseen barrier before us: a weariness that is in the heart more than in the limb.”

Bookie Details
– In the movies we see the tree hunters run next to a valley and you can see a river at its bottom. In the books this is described as: “The dale ran like a stony trough between the ridged hills, and a trickling stream flowed among the boulders at the bottom.”

Mistakes:
– Legolas’ eyes may be keen, but he seems to lack some sense of direction. From where he is standing Isengard is North-West, not North-East.