For me (and I'm sure others are this way too), I watch a few anime, or play a few games that I just randomly find, and if I like a character, and think I can do it, I do it..There are those few that I liked prior to getting into cosplay, like Dragonball, Sailormoon, and so on that were out when I was a kid and had no idea what cosplay was..As a kid, a big thing to do is always "what's your favorite character" (I mean that happens to adults too, but kids play around that way more) and I had some already that were favorites, and those ones are ones I want to cosplay now.