I try to remember the acronym, DATA: Dialogue, Action, Thoughts, Appearance. Here are a few show vs. tell examples.
Shelly yelled insults at Kathy. -vs- "You're a real bitch, you know that?" Shelly said.
Bill and Tommy got into a fight. -vs- With fire in his eyes, Billy clenched his fist and rammed it into Tommy's jaw.
John thought of his wife. -vs- I wish Marry were here. She'd know what to do.
Tom showed up to the party dressed like a pirate. -vs- Tom wore an eyepatch over his left eye and an oversized hat with a skull-and-crossbones on his head. His red coat nearly reached to the floor, and it flowed behind him like a cape as he made his entrance. On his belt hung an old, flintlock pistol and a buccaneer's blade. No doubt he'd have people walking the plank before the party was over.
Notice how in each example I moved from a general statement to something more specific and vivid. There is a time to use "tell" and a time to use "show." Anything really important to your story should be "shown", but If you just want to get information to your reader quickly so you can get on with the good stuff, then "tell" is useful for that.
Hope that helps.