Alright. When I first created my manga, I sketched out character designs from animes. I'd pause the dvds or vhs' and I'd just start sketching. I would take some clothes, and some hair, and just put them on a body. Then I would sketch that body.
Also another thing that will help is read manga all day. Make sure you pay close attention on the detail and the eyes/nose/mouth, or the bodys. Then try to just sketch them on paper, then do the full drawings. It's like doing character design first.
And also like from what inkhana said, you can check out
http://www.howtodrawmanga.com If none of those help, you could always get a trainer. If they do that in America.
