I found the concept of show not tell hard to grasp when I began writing. After all, isn't everything we write telling? The concept still frustrates me when I don't recognize too much telling in my own stories.
When we write we want to avoid making simple statements that don't add any details to the piece.
For example: The man was happy.
The sentence only tells us his emotional state. Instead, paint a picture and describe the man's happiness. His gestures, actions, expressions will help the reader see him.
Here is a showing example for the above sentence: The man hummed his favorite song as he bounced across the parking lot.
Telling example: The room was a mess.
Try describing the items in the room that make it messy and how a character might react to it.
Showing example: Jack stepped over the an empty pizza box, dirty underwear, and used tissues that littered the floor.
Telling example: John was mean to Jill.
How can I fix this telling line? I can by showing what John did to Jill.
Showing example: John clenched his fist and pounded Jill in the arm, leaving a bruise the size of a tennis ball.
Telling example. Drapes covered the windows.
It is better to show someone acting upon the drapes than to tell the reader about the decor.
Showing example: Margaret parted the velvet drapes, letting the sun inside.
Telling example: It was hot outside.
Pick out some details that show the effect of how hot it was.
Showing example: Perspiration rolled down her back, and she tugged at her damp top.
Telling example: It was icy.
Add details to the writing.
Showing example: Her foot slipped on the ice covering the sidewalk, and she tumbled to the ground.
Use senses to show and not tell. Touch: How did something feel? Smell: What did it smell like?
Hearing: Describe the sound. Sight: What did it look like? Taste: What was the texture, temperature, flavor? Describe a character's action upon, perception to or reaction to surroundings, weather, and situations to better show the reader your story.
The word was doesn't help to show anything. Look for was and consider revising the sentence if an opportunity to show has been missed.