Put your shadow into the picture, whether it be by sunlight, artificial lighting or other means.
Look for interesting surfaces that can really add to the overall shot for your background and include anyone else or anything else for added shadows
in your image too.
This is an exercise to stretch your photographic awareness
so creativity counts!
Let's see what you come up with...
- Dan
PS: Here are some examples: http://www.pbase.com/camera0bug/shadows