Plan your story! Sometimes random ideas aren’t that intriguing. (sometimes they are… but only sometimes…)
I’ve started thing of a basic idea of the story and the main characters. After that I’ve started to design the single chapters of the story with a few notes. Note the plans for first few chapter down and look if it fits together. Whenever you have ideas, which sounds good note them down and check if it fits to the story line, if not you can try to change a few things about this idea.
To make a story more realistic, think about the main characters, etc. and image a character type for them (like badass, good girl, nerd, athletic, etc.). After that let them act like their character type is!
For other realistic parts, get some information about different things you want to tell in the story (For example, in my story I’m talking about a specific sickness and because of my family I have experience with this)
Intriguing: Well, you can leave a few open questions, but some people like this and some don’t… For this you should do, what you would like!