Ah - never really got into anime, it was always flesh-and-blood guys for me. Which made it harder to figure out what the feelings were, since the hormones started firing for both groups.
I decided eventually that if I was intensely obsessed with a precocious nerdy boyish-looking Western European with a savior complex, I probably wanted to be him, and if I was obsessed with a slender dark-haired cynical Eastern European or darker-skinned guy with a biting sense of humour, I probably wanted to be with him. That's a purely empirical division though, based on the fact that relationships with guys from column A are totally weird and awkward and involve an unhealthy amount of imitation and obsession on my part, whereas column B has been stable with lots of chemistry. Certainly nothing I could explain (or even be consciously aware of) as a 13-year-old watching Star Trek with my parents.
I stll haven't figured out where to file my very close friends whom I develop "crushes" on (i.e. think about a lot, want to spend far more time with, have some "falling in love" symptoms minus the sex/romance angle) as the friendship develops. I think that might be a third category, but I'm not sure what to call it.