You need to design the game for your players. This means choosing a theme that they'll be interested in, and making sure that the puzzles are at the right level of challenging.
For example. if you're having an adult party, designing a game with a Frozen or Toy Story theme will leave some players checking their watches, sports scores, and Facebook feeds. (And hopefully, not writing reviews of your party on the spot!)
As Abraham Lincoln said, "you can't write an escape room story for all of the people all of the time." By considering your attendees, you can conjure a theme that will intrigue most of them and will amuse the rest. Your guest list is the starting point for this adventure.
Let's assume you want to throw an escape room game for an adult friend who loves the Great Gatsby. A 1920s themed murder mystery is just the ticket! Set your players at the scene of the crime and see if they can catch the killer before it's too late!
If you're having trouble coming up with a story idea, try cross-referencing your guest list with this list of exciting escape room themes
. Don't worry, nobody expects an original idea (and the classics are fun for a reason!). Then, move onto the next step: