I see this question all the time in writing groups, and the answer is: However works best for you!
There is no one answer. What works for me may work for you, or it may be a disaster. I recommend trying different techniques, and seeing which one works best!
But! I can tell you my technique, and how I developed it.
In the early 1980s, I came across a game that would change my life. A game that would help me become a better storyteller, writer, and planner. That game was Dungeons & Dragons!
Telling a story in D&D requires a bit of planning. I was often the Dungeon Master, or DM. My friends were the players and were the heroes of the tale. But for my friends to have their moment in the sun, I would have to prepare for the adventure beforehand. I would follow a three-step process: Create my Villain and establish his goals and agenda to obtain his goal, create the setting where the Heroes would battle against the Villain and his Minions, and finally, create a way for the Heroes to find their way to the Villian.
Creating the villain or Antagonist is a lot of fun. He or she gets to be over-the-top, utterly ruthless, and scary. Grand Moff Tarkin was the commander of the Death Star, but he’s not the one you remember. It’s Darth Vader who sticks in your mind!
After that, you need to create a place for Our Heroes and the Villains to battle. Dungeons & Dragons made it easy by putting the word Dungeon in the title.
But not all “Dungeons” need to be underground lairs. Pirates have ships and islands, Kings have castles, and Wizards have Towers. It has been a good idea for me to draw or create a map, and have notes to myself where the Villain and his Minions are located normally. This way, when I begin writing my Heroes I know where security is weak, where the Minions can ambush the Heroes, and where the Big Bad Evil Guy will make his last stand.
After that, I have to introduce the Heroes to the story. How the Heroes enter the story is critical to how they are likely to respond to the BBEG. Some heroes find hidden messages, others lose family or friends to the Villain and his Minions, and some just come across an advertisement asking for help.
Once the Heroes hear the Call to Action, The story itself can begin. But that is an article for another time.
See you next week with How Do I Write a Book, Part 2