It's been said many times before. It's practically one of the first basics that every writer learns, that every mentor teaches, and that every critic jumps on. That is the idea of 'show, don't tell'. And yet, while many people may hear that, to some it's a bit unclear as to what that really means, or how to achieve that particular goal. Hopefully, this would give you a slightly better perspective on what appears to be a very simple task on the surface, but actually takes a little practice and finesse to pull off correctly.
The first thing to pay attention to is the difference between showing and telling. The 'telling' part of the equation is simple...these are the details of who your characters are and what's going on during any particular scene. Telling is a vital part of writing, so even though people say 'don't tell', don't think of telling as being the enemy. Telling is describing what your character is wearing, the color of his hair, how clean or how messy his bedroom may be, or whether or not it's raining outside. These are all things that your readers are going to need to know if they want to fill out a complete picture in their minds. You can also use telling to describe a certain action. Use it to let your reader know that your character crossed his arms, or that he gave your protagonist a slightly goofy grin. Maybe he's shuffling a deck of cards while he's talking or sipping beer out of a plastic cup. These are all acts of 'telling' your audience what they need to know and giving them a clear vision of where they are and what's happening.
Now 'showing' is a little bit different. Showing is the talent using the basic details and actions above to tell a much deeper story. Think of telling as getting the ingredients, spices, and garnishings together for a gourmet dinner...and showing as actually having the skill to use those ingredients to make your dish a masterpiece. Sometimes, this is where some people get a little shaky, and if you try to cut corners on this part of the process, you'll be missing some of the emotion and reader involvement that you need to make your story memorable.
Let's say you have someone in your story who's a friend of the main protagonist...but he can be a real jerk sometimes. Now there's nothing wrong with describing him through narration or simply writing, "He's my friend, but he can be a real jerk sometimes." That's perfectly functional, but that's just you 'telling' your readers that he can be a jerk. How do they know that? What are you going to do to demonstrate that? Simple...you create situations in your story (Even if they're very small scenes) that actually show him being a friend and other scenes that show him being a jerk. Maybe you have a small scene where he stands up for his best bud against a bully, but in the next scene he runs up and smacks the books out of his hands because he think it'll be funny. Just a few actions like that will give your readers the information they need about the character, and you won't have to waste time 'telling' them that. Find ways to use your story to actually demonstrate what you want your readers to know. Instead of saying, "He was so beautiful!" try creating a scene where your character is just caught off guard and keeps looking back at him. Describe his eyes, his hair, his laugh. Create an infatuation that your readers can feel and take part in. Just saying 'he's beautiful' isn't going to be memorable or important later. But readers will definitely remember that scene and think back to all the times they've felt the same way. It builds a stronger connection to what's going on.
This works for everything. Moments of heartbreak, sadness, anger, and joy. Your characters' actions and spoken dialogue should say more about them than just what you type out on the screen. Every time you're describing something that isn't just concrete details...ask yourself how you can prove to your readers that the statement you just made is true. If you call someone a tough guy, or say that they're really funny, or that they seemed really shy and uncomfortable...ask yourself if you can find a way to demonstrate that through their actions instead of just saying so. Someone who's shy might look down at the floor when he talks or blush when given a compliment. Someone who's sad might seem distant or might be heard sniffling softly in a corner all by themselves at a party. Don't be afraid for your characters to speak for themselves and show who they are without the extra help.
I hope this helps a little bit and gives everyone something to think about while you're writing or editing your next story. A few well-written moments in your story will create memories that your readers will cling to and remember. Unless you've just written one of the greatest, most quotable, sentences in the history of literature...no amount of simple words and details will have the same effect.
Then again, if you can do BOTH...then go for it!