0.7mm and 0.5mm mechanical pencils, printer paper.
eye-copy from Asano Inio's Oyasumi Punpun.(original)
Many people will tell you that copying is bad. It is. It's really sad when someone takes your artwork and claims it's their own. I'd know, it's happened to me a few times... But I think copying can be good, as long as it's only meant for practice or learning.
There's a certain experience that you get by eye-copying like this. In pencil sketches or when imitation a CG style, I've learned that this is probably THE BEST way to learn an artist's style. Like this, I learned Asano Inio's lines and curves, the way he draws specific things, and the overall process of his art. Asano is my favorite artist and inspiration at the moment, so I was very happy to learn how his art worked.
