The first step is to study the image you are starting with. Be it a lovely picture of Natsumi, or a tree, or this morning's breakfast. You should study how the light constructs the image.
Examine what is light and what is dark. Decide what you want in the image... Nacchi's face... the leaf she's holding... the blurry background... Remember you are the artist, you can add or subtract whatever you want. You can have a leaf and a blurry background ^__^