I'm wondering what makes an otaku? What does it mean and how do I know if i am an otaku.

Umm..Maybe you should check out this thread dude.

** [color=green]Mad people either have no sense or too many extra senses... [/color]**
[color=red]On the net, men are men, women are men and children are the FBI. =D[/color]

Absolute obsession over anime/manga and other things related (ie. games, posters, figurines, etc). It means cosplaying, using all your salary on your anime/manga collection and basically living and breathing anime/manga. You keep everything you collect in mint condition and you know everything there is to know about your preoccupation.