i wish i had a secret to give to you dear anon, i’m afraid it’s mostly just making observations and finding patterns in behavior and interactions. i think the important thing with having strong characterization in your writing is just trusting your readers. you don’t need to spoon feed every single detail you’re trying to get across in explicit detail. sometimes the best way to build a full and realistic character is to let certain things be assumed instead of stated directly. it’s also just based on vibes more than anything else. i have full confidence in the things i say and write about no matter how delusional or detached from reality they are and i think that comes across in my writing. trust yourself, trust your writer, pick an assumption and just run with it until it feels correct to you.