That is actually pretty tough.
I mean it would help if the person could really understand the morales behind anime/manga, going past the general storyline.
Cosplaying really shows your colors as a real otaku. From what I have read about it a lot of research of the characters looks is involved, on top of making the complex costumes.
Ah another thing, not ashamed to admit his love for anime/manga amongst a crowd of haters. (I am about the only person at school who like anime it seems -_-)