1) Plot Notes
For me, these are usually only a few sentences, noting any key points I wish to include. However, some people like to plot in much greater detail before setting pen to paper or fingers to keys. See what works best for you.
It is helpful to have a clear understanding of your characters before getting too deep into your tale. Otherwise, how can you write them without introducing conflicting representations? How in-depth your profiles go will depend on your needs. I have a ½-page profile I fill out for each main character in short stories and a three-page one for characters in novels and novellas.
If this is a story idea that simply came to you and which has no end date or destination in mind, you won’t need to worry so much about this final point. However, if you are writing for a particular publisher or, more importantly, a particular open call, you’ll need to note and keep in mind details such as required word count and submission deadlines. I do this in a tracker in my bullet journal, but you could also create a basic spreadsheet to capture the pertinent details.