There are many ways to improve your writing — and it doesn't matter what style of writing: fiction or non-fiction.
Let me lead you down the rosy path.
If you feel you are impressing the reader by writing long sentences that drag on with rambling thoughts or ideas; you're wrong. In fact, the last sentence could be re-written to: Long sentences don't impress readers. Rambling thoughts or ideas drag out the process.
So keep your sentences short. A fiction writer could offer:
They heard the gunshot from the other room and stared at each other before reacting and dashing to see what had happened.
But, with shorter sentences, more impact could be offered.
A gunshot. From the next room. Bill and Jane stared at each other then dashed to see what had happened.
Now, for the non-fiction writer, let's use a sports article:
Harris, number 18, with time running out, dribbled and shot the ball toward the net, watching it rebound as the buzzer sounded.
Rewritten with shorter sentences —
Harris, number 18, dribbled the ball. Time was running out. He shot. The ball rebounded as the buzzer rang.
Notice how, in each example, the 2nd sentence, the impact is more intense? By using shorter sentences, the writer can imply urgency. But, not only that, by using shorter sentences, the writer also can relay the information better and clearer.
Nothing is more boring than reading page after page of passive voice. It is all "has-been" action. For the fiction writer:
The dragon had come from the north mountains and the village was scorched by its fiery breath.
By re-writing it to an active form:
The dragon flew out of the north mountains to scorch the village with its fiery breath.
Many non-fiction authors (scientific journals) seem comfortable with passive voice and should learn to avoid it to punch up their writing.
A number of findings are indicated by these results from several surgeries.
The above can be more exciting to read as:
The results of several surgeries indicate these findings.
Most new authors don't realize a little secret. White Space. In fact, many author veterans don't understand this secret. A large paragraph of words can be impressive on a page. Yes, it appears you have written well, but in reality, you've caused a massive collection of letters that most readers will find daunting. They will "glaze" and skim over the paragraph, grabbing what they feel are important words. In fact, I've deliberately created this monster of a paragraph as an example. Notice all the white space before and after? It reads faster and this has slowed you.
Now, trying it with white space added and a small modification.
Most new authors don't realize a little secret. White Space. In fact, many author veterans don't understand this secret.
A large paragraph of words can be impressive on a page. Yes, it appears you have written well, but in reality, you've caused a massive collection of letters that most readers will find daunting.
They will "glaze" and skim over the paragraph, grabbing what they feel are important words.
Notice how much easier this is to read? It reads faster. White space is your friend.
Generally speaking, it is just as if I had dropped the ball that I always hold when …
In the above sentence, there are several "weak" words - generally, just, as if, that and always.
The sentence could be re-written as:
Basically, I dropped the ball I hold when …
By ridding the sentence of the weak words, the sentence becomes stronger, has more impact and is clearer to understand.
Another way authors weaken their writing — the use of a modifier to "enhance" the word said. Yes, the adverb to modify a verb.
"Stop!" he said urgently.
In the above example, show, don't tell.
Tom saw the car racing toward the children. "Stop!" he said.
Show the urgency, don't tell us it is urgent.
As a writer, you are also a reader. As a reader, you know you skip segments when you read. Analyze why you skip certain parts of the book, article, short story you are reading. Now, don't write those parts.
These aren't the only things you can do to improve your writing, adding impact to your novel, article or short story, BUT these will get you started.