The adage "show, don't tell" has always struck me as a confusing one. After all, it's talking about writing and, when we write, we by definition tell: I have told you something in these two-and-a-half lines of type! Maybe a better way to say it (I forget the person who originated that adage), is "demonstrate or illustrate, don't explicate or explain." Here is explaining: Josh was arrogant and vain because he had the best free throw and the best hair. He never even said hello to a studetn who wasn't a Varsity athelete. He never said "Excuse me" when he bumped into someone in the hall.
Here is demonstrating or illustrating (I hope): Josh climbed out of his Mazda MX-5 Miada, stormy blue to match his Varsity jacket. Though his tastfully dissheveled hair was perfect, he ran a hand through it as though to improve it, knowing you can't improve perfection. Timmy, the Sophomore ball boy for the B-ball team, walked past Josh, as every morning, and called out a hopeful, "Good morning!" as every morning, only to be greeted by a blank but condescending stare trimmed by Josh's perpetual smug smile ... as every morning.
Well, you get the drift. The first one, explicating/explaining, is equal to "tell." The second one, demonstrate and illustrate, is equal...
to "show." In the first one I told you that Josh, an athlete, thinks he's cool. In the second one, I showed you that he thinks he's cool: arrogant, vain, unfeeling, rude, inconsiderate. I "show" this by putting Josh in real-life circumstances and letting his inner being take over and show itself off: his car, his car color, his hair, his stare at Timmy; his Varsity jacket.
This beginning for "athelets who think they are cool" should get you started and provide you with a clearer understanding of what "show" and "tell" are actually about: demonstrate/illustrate and explain/explicate.