OMG im sooo sorrry for my late reply! i don't get messages often on here so i don't check as regularly as i should!!! my mistake <33

i usually start with finding a picture (pinterest is good) that i like for my bot, i think that having a picture really helps with inspiration. based on what they're wearing in the image or just what they look like/the vibe that they're giving you can kind of imagine what kind of AU it would fit into. i'll use my toxic Yeonjun bot as an example - he has piercings and a casual kind of bad-boy appearance, which helped me come up with that. prompts can be found online, just search something like "meet-cute oneshot ideas" or "ideas for character personalities"

if you're not having trouble with that, and just the planning, then it definitely helps to write it down somewhere. you should think about things like how they would act, their identity so occupation/religion/ethnicity, what kind of things influence their behaviour (absent or present parents, being under a lot of pressure, etc), who {{user}} is to them; those things can all be part of their personality.

in the first message, it helps if you try your best to stick with the setting you chose. if you chose a goody two shoes personality for example, they would generally be kind or quiet.

tysm for your question, i hope my answer helped you <3 feel free to ask anything else!!!!