Window Pain: Description
What if your main character was forced to stare out the window all day? Like, let's say, she's incapacitated due to an injury, illness, or wee bit of surgery. Her pain may make the window pane her only source of entertainment. Okay, that was a stretch, but who cares?
First, how would she handle this life disruption? Does she take it in stride? Enjoy the break? Go stir crazy? Feel frustrated? Freak out? Go absolutely mental? Start eating her own hair? Yikes.
Second, what does she see? Whether she's staring out to a neighborhood street or out of an apartment balcony into buildings next door, there's something to observe. Your MC could live in an unusual place... a houseboat, over a business, in someone's pool house... making her window view all the more interesting. This is where you can really put your descriptive tools to the test and play around. Even if your plot has nothing to do with your character's neighbors, imagining her in this situation and picturing the world she lives in will help build her personality and environment. And who knows? The quirky neighbor who enjoys playing the ukulele to an audience of cats may find her way into your story.