Really for me it was through using the tags to search through articles of things I liked. I really like video games and music so I started going through their corresponding tags, found people I liked and started following them and rather quickly I had found a few really good communities.
I was also fortunate enough to have a few key people comment on my posts that had similar interests to me. So from there I looked at what they were resteeming, contests they were entering/hosting, what they were posting about and who was commenting on their posts and pretty quickly I had found my place on Steemit!