To draw first of all you need a lot of patience. If you try drawing something and it doesn't look to good, you have to try again and again, till you get it right. Copying, as Rei said, is good excercise, especially for poses and details of body parts (like hands, which I find particularly tough to draw
). After that you can start with coloured stuff. If you have a scanner and a decent program, you can try to add colours with the help of your PC, which is fun and easier than using other media, like watercolours or markers.