Any good writing teacher will give you this sage advice: Show, don't tell. I, too, offer those words of wisdom! Apply them to everything you write.
For example, suppose I write this sentence: "My ten-year old sister is very fast!" That sentence tells; it doesn't show. How do you make those words show? Well, you might say, "As a garbage truck passed our house, my ten-year old sister raced it to the corner of our block. She took off in her brand new, white Nikes, her braided pigtails flying, and she beat that truck by two garbage truck lengths! The trash men whooped and hollered all the way, telling their driver to 'step on it!'"
Or, you might write, "My girlfriend really loves me." Again, this is a tell sentence. How can you make it show? You might write: "My girlfriend handed me two 40-yard line Steeler tickets for the Cleveland Browns game and asked me to take my brother. Then, before she drove away, she handed a six pack of Iron City beer out her car window and drove away saying, 'Have a great time, honey!'" Here in Pittsburgh that would be called "true love!"
How does this concept apply to business writing? For one thing, it applies directly to resumes. As I have reviewed hundreds of resumes written by my students, I typically see language like this: "Coordinated a team of project engineers for the installation of customer relations management software at Widget International."
That sentence will provide more meaning and create more impact it if says, "Coordinated a team of seven project engineers in a three-week engagement at Widget International of Buffalo, NY, to install customer relations software and increase customer satisfaction scores by 11.5%."
When you tell, you rob the reader of scene, story, and outcome. When you show, you give the reader the scene, story and outcome. Every sentence we write may not include an outcome but everything we write is story. We introduce ourselves to a potential client and we tell a story. Better yet, we introduce ourselves to a potential client, and we evoke their story! We listen to their story. Then, after we understand our clients' needs, we share our stories; we build narratives that show how we have benefited some other customer. This works especially well in cover letters or executive summaries to RFP's.
So, if you're trying to sell your services to a customer or even sell yourself as a potential date, especially in writing, show, don't tell.