When you're writing, sometimes you want to start at the beginning. But when you're only at the writing stage, it doesn't actually matter if you start writing there! Sometimes it's best to start in the middle or at the end. Adventure is one of those times.
Because adventure is about change, sometimes it is best to start with who you want your character to become (or the aspects of yourself/character experiencing change that you want the reader to see) rather than beginning with how that character began. Two of the reasons for taking this approach show its clear benefits:
- By emphasizing the traits which the character develops through the quest at the end, you can be certain that when you write the beginning at a later date that you pick actions, descriptions, dialogue, and scenes that illustrate either the absence or opposite of those traits.
- By recognizing what has changed in the mind and actions of the changing character, you can make certain to highlight those moments of high action/drama with the thoughts/reasoning of the main character which brings him to the conclusion that he draws. For example, a car accident in itself is not enough to make anyone come to any conclusion. It is the rationalizations and reactions to the car accident that cause the protagonist to forego all future driving, decide to get driving lessons, or develop a feeling of immortality. We all react differently, and it is not enough to show the event and expect us all to arrive at the same conclusion (yes, I know "show; don't tell," but you also need to show the thought process or we may miss your point! And, honestly, the longer I live the less obvious I think it is that people will just understand. Most of us don't. Really.).
- Write the scene that's bouncing around in your head first. It should come out the most easily.
- Write the ending you would like to see, one that you feel will make you feel "full," as if you've just finished an excellent meal.
- Write a simple description of your character's philosophy/outlook on life at the end. Then elaborate on that feeling by expanding those ideas to how your character's appearance might reflect those feelings--what bumper stickers would he have? What kind of car would he drive, shoes would he wear, place would he live, etc.? Then expand that to dialogue. What jokes would he find funny now? What things would he say or NOT say? Finally, channel that into actions. On the basis of his inner changes, what outer behaviors would manifest themselves? What would he do if a homeless person begged him for money, if he had a gun in his face, if he was given incorrect change?