omg i have such an in depth way of keeping track of my ideas and plans and what not it’s kinda ridiculous lmao but the main thing i always do (esp since i usually only write fics for shows) is that i tend to break up my notes by episode. so for example i’ll have “episode one” and then bullet point every thing i have planned for that ep(or just little things i want to mention, dialogue i want to include etc). for my hotd fic the universe is very lore heavy so i also have sections boldened( ie, how valyrian marriages work, locations in westeros and their lore, just general targaryen lore etc etc), so i dont forget important tidbits/things i might want to mention down the line, and then in bullet points below it go into pretty extensive detail about said thing. essentially just bullet point anything and everything that you might have in regards to plans, your oc, canon characters, whatever. it keeps everything quite organized at least for me!