Double duty: is your writing pulling its weight?

I've been reading Characters, Emotion & Viewpoint by Nancy Kress, published through Writer's Digest Books, and I've been noticing a common theme. No matter what you're writing, whether it's setting, dialogue, drama, backstory, etc., Nancy encourages you to always make it do double duty, thus maximizing your word usage and the impact of your writing. 

Wow! I thought. Great idea! Then I began to wonder if I did this. The unfortunate answer was not often enough. In fact, I realized that the only time I was applying this powerful double strength writing was when I was doing it unconsciously. If I wanted to be published someday, I couldn't afford to miss out on this opportunity to make my writing better.

If you're not sure what I'm talking about with the double duty thing, here's an example. Say you're writing a scene which shows your main character trying to obtain an after-school job. Here's a paragraph that focuses on setting:

The bell jangled above Isaac's head as he pushed open the worn wooden door of the pet shop on Main Street. After his eyes adjusted to the dim interior, he threaded his way through a clutter of dog toys, bird cages, and pet food until he found the counter at the back over which the grey-haired owner Mr. Stanford  peered at him from under his shaggy eyebrows.

We've described the pet shop in which Isaac has chosen to look for a job, and we've even described its owner a little. There's nothing wrong with this, but could the description do more? Could we write this description in such a way that it actually does double duty and also paints a picture of Isaac's character in the bargain? Let's try again.

Isaac pushed open the worn wooden door of the pet shop on Main Street and jumped as the bell jangled above his head. He shuffled from one foot to the other, waiting for his eyes to adjust to the dim interior while he got his bearings. After a hesitant cough, he threaded his way through a clutter of dog toys, bird cages, and pet food until he found a counter at the back over which the grey-haired owner Mr. Stanford peered at him from under his shaggy eyebrows. Isaac swallowed a couple of times and opened his mouth, but no sound came out.

Ta-dah! Now we know where we are, but we know some things about Isaac, too. He's timid rather than bold and cocky, and he comes across as cautious. It would seem that he's either not comfortable when talking to adults or that he doesn't know Mr. Stanford well. Possibly he's a little scared of him. Even without the skilled hand of Nancy Kress, I've made my little setting do more work than it did before.

How about you? Are there ways that you can consciously get your writing to do more?