This is something I wrote:
The person was standing in the middle of the clearing, facing away from me. It was a girl. She was wearing a red knit hat, a white sweater, an a gray plaid skirt that reached right below the knee. What was she doing here, alone? I looked up, and realized she was gazing at a huge ancient tree. It was as thick and tall as a watch tower. Its branches resembled arms, and the leaves were so few you could count them with your fingers.
As you can see, that paragraph is filled with the passive voice.
So I tried changing some into the active voice:
The person stood in the middle of the clearing, facing away from me. It was a girl. She wore a red knit hat, a white sweater, an a gray plaid skirt that reached right below the knee. What was she doing here, alone? I looked up, and realized she gazed at a huge ancient tree. As thick and tall as a watch tower. Its branches resembled arms, and the leaves were so few you could count them with your fingers.
Did that improve readability? When to keep the passive voice?