I think a great advice is that pixel-art isn't separate from the rest of the art world. Basic knowledge of form, structure, perspective and so on is necessary in painting as much as pixel art.
So I wouldn't suggest you start drawing pixel-art if you haven't go a lot of experience in the more basic art forms - just drawing. In essence, pixel-art is stylization. If you'll know how to draw and construct a human shape with pen and paper, chances are you'll be able to do the same in low resolution pixel-art.