Select a portion of the picture that interests you, crop it and play with the values and colors to determine what would result in a good composition. If you have Photoshop, it’s helpful to apply the "Cutout" filter to break you picture down into distinct shapes. If not, you can think about how you want to group you values into an interesting arrangement of darks, mediums and lights.
Please be sure to follow the spirit and the letter of the challenge.
For example, each submission must be painted after the challenge is posted.