Well pretty much everyone's giving the same/good advice so I'll just throw this in there: look up video's of people drawing. I watched speed paints on youtube for fun for a few years and then recently found out that I'm not that bad at trying myself. True, I'm not exactly Da Vinci but from going to maybe doodleing every now and then in class to at least having the hope of becoming somewhat good... that's something, at least to me.
The point, look up video's of people drawing and study them. I digitally also traced as well for a little while but I was only doing it for fun and wasn't serious enough for it to probably have any effect.
Here's a good digital speedpaint to go on:
pt. 1 http://www.youtube.com/watch?v=9j3V6BQUbmQ
pt. 2 http://www.youtube.com/watch?v=B7GQprmID9I
Traditional:
http://www.youtube.com/watch?v=OE-vDtgw9XE
It's harder to find good quality traditional speed-drawings but if you keep looking I'm sure you'll find them ^_^
This person is actual a published american manga artist. He has tons of how-to draw tutorials so be sure to check them out! http://www.youtube.com/user/markcrilley
Just keep looking up more video's, as well as differences on proportions, anatomy, eyes, art style etc. Deviantart is seriously my favorite website EVER and it has a ton of great art and artists that you can learn from as long as you look so be sure to check it out :)
Well, I hope that helps! And good luck with your project!!!!!