Next time you watch a movie where people have to do some walking, take notice of where from and to the characters are walking. Chances are, most times the good guys will move from the left side of the screen to the right side of the screen. A good example of this is Lord of the Rings, because there's a lot of walking. Heroes are almost always walking left to right, while the orc armies march from right to left.
Rogert Eberts explains that movement to the right is considered positive and to the left negative. This is because the eye tends to read a picture from left to right, and so physical movements in that direction seem natural, while movements from right to left seem inexplicably tense and uncomfortable.