I found pictures of people online whose body and hair looked similar to mine and then found ones with outfits I liked and used that to define my style goal. Basically, I copied other people
And then over subsequent years, and now even, I'm not looking online so much and am just trying to feel things out on my own. For example, this summer, I seem to like sporty looks more than boho (although I like both these looks) so my style direction this year becomes "sporty". I guess what I'm saying is that my style direction now follows my mood.
When I was first starting out though, it was definitely more methodical and logical.
I've only really been paying attention to clothes for the past 4-5 years though so I'm still a newb!