Through the course of working as a literary journal editor, I've noticed a trend in the stories that I reject. They do a poor job of establishing the stakes of the story, and I ask myself why is the story being told in the first place? Why do I care what happens?
For readers and viewers to be involved in the adventure, to care about the hero, they have to know near the beginning exactly what is at stake. What does the hero stand to gain or lose in the adventure? What will be the consequences for him if he succeeds, if he fails?
Stories often fail because the stakes simply aren't high enough. A story in which the hero will be only slightly embarrassed or inconvenienced if he fails is likely to get the "so what?" reaction from readers. The stakes need to be high -- life and death, the safety of a lover, treasure, or maybe even the hero's soul.
Having high stakes creates drama and tension. If the reader fears for the safety of the hero, then they are more invested in the trials that they face. Think to your favorite fairy tales and folklore. The stakes are waved in front of us like a glittery, flashing banner. In Disney's Beauty and the Beast, Belle chooses to stay with Beast in place of her father, because if she doesn't her father may die. On the flip side, she may die in his place. In Disney's Aladdin, the young street rat chooses to help the creepy old man retrieve the lamp, because if he didn't, he would stay in prison and surely be executed. For Belle, her father's life is at stake, swaying her decision. For Aladdin, his life is at stake, swaying his decision. The greatest stakes are life and death, but the stakes can be more abstract: personal freedom, peace of mind, the granting of a heart's desire... etc.
Take a good look at your work in progress. What are the stakes of the story? Why is the story being told? Why should the reader care what happens to your hero? If you can't answer these right off the bat, then maybe you need to work a bit harder establishing what is at stake.