You dont need to have great talent to draw.
It requires great deal of patience and compassion.
Drawing is just a technical skill, which can be improved over time just by hardcore practicing.
Like previous poster said, study the human anatomy first if you wanna draw manga. That is the very basic. Dont just draw pretty eye, faces and stop right there. You can also draw your own finger, hand just by observing. Slowly develop the sense of human anatomy. See the muscle etc etc. This is very important. You can started off by drawing random figures from magazine, and also manga but i dont recommend it. Manga is just a stylized figure and should not be a reference. However, the angle of projection, styles can be reference from manga.
Once you got the basic right, you can proceed to create your own style of manga. And there is where TALENTS comes from. CREATIVITY.