First time I joined a fandom, it has been a slow, gradual process, with years upon years of build up and a late realisation.
Well, several, I guess. I was obsessed with more than one fandom at the time, I just had to get lost on the internet to realise fandoms were a thing. Anyway.
Forelast time I joined a fandom, the fandom was as good as courting me. The fanart showed up anywhere and everywhere I looked, interesting crumbles of information were left on my social media, and I finally let them have me after I noticed I was already shipping Destiel. (Yes, Supernatural, I am looking at you.)
And last time, well, I might or might not have been low on fanfics, so I sort of looked up a fandom that had books and had lots of stories and crossovers and then I just casually picked out a few ships and marched right into it.