Yoshiharu,
Basically I obtained as clear a print of a painting as I could find and began to copy it using the underpainting technique. And at first it was very difficult for me to do. I finally settled on an Old Master palette and this made all the difference. See:
http://forum.portraitartist.com/show...=&threadid=210
Sometimes, after I did a copy, I was fortunate enough to be in a Museum somewhere and view the original. It was nearly always a rude shock. Although my paintings looked like the print I copied from, the prints seldom looked like the original painting!
Despite this drawback, I learned to paint anyway. I really can't think of any special prepartation...just pick up your brush and begin.