If I’m not entirely sure about which way to go with a story I’m working on, I ask for suggestions from one (or occasionally two) of my fellow writers. If the story is a fanfic, then I approach someone who is familiar with that fandom.
For example, I’ve been having a PM dialogue with GrayNeko about a Big Hero 6 story I’m doing preliminary work on. I’ve asked him for suggestions about the science-y aspects of the plot, bounced ideas off him regarding including music in the story, and kicked around thoughts about the title. He’s been a big help.