- Determine the general setting--"space opera", "sword and sorcery"
- Determine the "Hell Yeah" moment--the moment at which, if your novel becomes a movie, everyone in the theater will cheer. Example: the outmatched hero suddenly turns out to have powerful allies
- Decide why this needs to happen right now, rather than when we're in a better position.
- Work out who does this to whom. Examples: a lone smuggler to the police fleet; a dispossessed king to an orcish army. NOTE: the do-er has to be the hero, not some deus ex machina or other third party.
- Work out the details of why the bad guy was trying to do this. Example: stop the smuggler from getting news out; capture the city where he thinks the McGuffin is.
- Work out how the hero gets to be in a position to pull off this stunt. Examples: he's found the barbarian fleet himself; he's the king who inherited an oath from the ghosts.
- And you end up with Serenity leading the Reavers into the Alliance fleet, or the Galaxyquest ship drags the mines into the Big Bad ship, or Aragorn leaps out of the corsair ship and the ghost army materializes before the orcs
Examples of "hell yeah" moments:
- Lone hero with bomb gets close and destroys monster. Star Wars, Monster Hunter International, A Hymn Before Battle
- Types of Hell Yes moments
- More examples from TV Tropes