When watching a new series I find myself sometimes needing to hear character names a few times in a few episodes before remembering them, less so if they're the protagonists (obviously). It also sometimes gets confusing when first and family names are both used due to formalities and all that good stuff. I think I know more first names than full (both first and family) names. But when I used to bone Naruto I knew all their first and surnames, though I've forgotten most of them now as I haven't seen it in over a year.
But then again a lot of the time, there will be a character that really stands out to me and I remember their name easily. I guess it depends on the anime and which characters interest you the most.
What about you guys?