So, you've introduced your characters and your world. Or maybe you haven't. Maybe you skipped that part, and you're too excited about throwing them into the middle of the story to want all that slow build up. Either way, awesome! Here's our next element:
This portion of your story is called the "Trigger," or the "Inciting Incident." It's called that because it triggers or incites all the events that follow it.
As an example, let's take a look at Star Wars. Assuming Luke is our protagonist, the Trigger for his story is the purchase of R2-D2 and C3PO, because it's at that point that everything changes. Their presence and actions lead to the events that force him to leave his home, travel with reckless strangers, fight evil empires, and rescue princesses. (The golden age of sci-fi/fantasy, right there.)
For another example, we might look at Spirit; Stallion of the Cimarron. The Trigger for Spirit's story is the sighting of a campfire in the distance one night. His response to that sight leads directly into his adventures for the rest of the story (which include him leaving his home, rescuing a helpless human, and falling in love, among other things).
At the beginning of EVERY* story (or near the beginning, at least), there's a Trigger of some sort, moving the main character(s) out of their comfort zone and into the Unknown (which I will eventually discuss in depth).
There's not really much more to this particular element. It's an event, meeting, ultimatum, challenge, or rite that forces their standard for life to change. And it doesn't have to be directly related to the rest of the plot, either.
In Spirit, for example, the cowboys whose fire Spirit sees at the beginning of the movie are not responsible for or even directly associated with the military outpost he's taken to, the railroad he's sold to, or the Native Americans he's stolen by.
Once your Inciting Incident has taken place, the story can begin in earnest, and there are adventures waiting to be had just up ahead.
If you have any suggestions, requests, or questions for me, feel free to let me know, either by commenting below, or posting in the forum.
Until next time, stay awesome, readers.
*There is an exception to this rule: Slice of Life stories.
From my personal experience, Slice of Life is a genre that accurately depicts a section of a normal person's life, and it's often incredibly boring. At any rate, the French 1800's Slice of Life excerpts I read in college were among the most mind-numbingly uninteresting things I have ever read.