I like to have a general plan and play it out, but I’m not too specific with it until something happens in-game.
Then I have an entire concept.
Sim A will end up with Sim B, that’s what I imagine. Spice it up a little and move a jealous attractive fitness trainer next door to inspire a potential affair. But sometimes the Sims in my game are too strong and defy me by doing what they want (as they should.) I noticed Sim B always got up before work and would turn on the stereo, while Sim A made breakfast and honestly it’s just too cute that I didn’t want to break them up. I enjoy seeing what the sims are up to by themselves. Maybe it’s a harmless autonomous action like Evil Sim Enemy Number 1 sitting next to Attractive Fitness Trainer at the bar, but add a few glasses of ridgeports and simsmapolitans, and it becomes a partnership— an evil plot against Sim A and Sim B. ‘Cause maybe Sim A and Sim B are fabulously wealthy and are responsible for Evil Sim Enemy Number 1’s mother’s death. And maybe that’s how Evil Sim Enemy Number 1 became evil in the first place!
An entire storyline is formed simply because a sim sat next to another and hit it off with some drinks. That’s basically it.