This is done best when your client is able to bring in a small container or box that they feel represents them. Then introduce the activity if creating a collage on the inside that represents who they want to be. The outside will be collages with how others see them, or how they perceive others seeing them. I like to assign them the homework of calling or texting friends and family and asking for three words to describe them or for their first impression.
In its simplest form, fold a sheet of paper in half and have the client create a collage in the inside of the card and outside with doodles, magazine clippings and words.
Always engage you client in describing their work when they are finished! Have fun!