Pay close attention to -ly words (ie adverbs).
You could actually use many beautiful and extravagant words to caringly describe things.
Or, you can cut to the chase.
I'm not good at using adverbs anymore so forgive my sad attempts.
Whenever I'm critiquing someone's manuscript I circle all the -ly words.
Sometimes it's okay to use a good adverb. But, it's important to be aware of what you're writing and how you want it to sound. Toy around with words and see if you can write the same thing in a different way (only without the adverbs).
Watch adjectives too.
The big, ugly, hairy, scary monsters will eat you before you get the chance to describe them when you have too many adjectives. Keep it simple.
Let your verbs and nouns speak for themselves, and your writing will be much stronger.
Avoid using was -ing.
I was typing. (Now I'm not.) Gotcha! I'm still typing.
I was going to see a movie. (But someone died.)
He was talking. She was eating. They were throwing up.
First of all, if you use the was -ing you are using too many words and your writing is weak. Second, people might think something that isn't what you intended.
Instead say, I typed. I watched a movie. He talked. She ate. They threw up.
Show. Don't Tell.
This one is tricky. Because how do you show something in words?
The best way that I've found is to put it into scene.
Let us see it as it happens in the NOW.
Use tiny details. Someone shuffles their feet back and forth as they try to ask someone on a date. Someone tears at the hang nails on their fingers when they're nervous or bored.
Let the voice tell the story.
Here are some examples.
Tell: Hank is ten years old.
Show: Hank is such a ten-year-old boy. I've been here for a total of five minutes and he burps in my face.
Let the reader make the connections. Not everything has to be spelled out.
Tell: My little sister's name is Angie.
Show: They separated me and Angie.... I miss my little sister.
Tell: My mom didn't do it.
Show: "It's traumatic for anyone at any age have their mother go to prison," I say. Especially for something their mother didn't even do.
As you critique others, keep an eye out for some of these things and make comments.
One big thing to keep in mind is you don't have to tell a writer how to fix their problems. Just point out the places that need work. Maybe tell them that there are too many adverbs or they need to show this part rather than tell. Once they're aware of what needs attention they can go through and figure out how to re-write it.