Every day we interact with objects, places and sensations that affect the way we think and feel. This can be used to the writer's advantage by planting symbols in the reader's path to reinforce a specific message, feeling or idea.
Look at the setting and the character's state of mind, and then think about what you want the reader to see. Is there a descriptive symbol or two that works naturally within the scene to help foreshadow an event or theme, or create insight into the character's emotional plight?
Seasons: Spring, Summer, Fall, Winter
Dandelion fluff on the wind
Melting snow or ice
Snake shedding its skin
The Death Tarot card
A row of school pictures
12 step programs
Human growth cycle (height/weight changes)
Innovation & inventions
Drug/alcohol use (altered physical/mental state)
Shape shifters (fantasy)
The Greek letter Delta
These are just a few examples of things one might associate with Transformation & Change. Some are more powerful than others. A Butterfly's cocoon is a strong symbol, and likely will not require reinforcement. However, Crime could stand for a number of different things and may not foreshadow Transformation & Change on its own. Let the story's tone decide if one strong symbol or several smaller ones work the best.