Writers, keep this one piece of advice in mind:
"Never say in 10 words what you can say with 3."
One mistake I find myself making A LOT is being too wordy. I like to think that adding an extra word or two helps to add something to the sentence, something like gravitas, weight, an extra punch.
See what I did there? I made that sentence far longer than it needed to be to prove a point.
To be a good writer, it's time to cut your writing way back! You need to start looking for concise ways to get your point across, as that will make your work much, much better.
Think about this line:
"It was the best of times, it was the worst of times."
Short, pithy, and properly Dickensian. In that line, it basically sets the tone for the entire book. It tells you everything you need to know about the setup for the story, and it's just 12 words!
According to some experts, as many as 50% of writers make this mistake. Some writers could stand to lose a few thousand words, while others would do well to trim it down by ten, twenty, or even thirty-thousand words. Talk about editing with a brutal pen!
When you write, try to say as much as you can in as few words as possible. Keep your paragraphs short, your dialogue snappy, and your descriptions on track. Don't meander and give your readers too many details, but just give them enough to keep them hooked.
Once the writing is done, go back over it and start looking for words to cut out. If they're extraneous, cut them. If you can say with one word what you currently say with three, cut them. If they don't add to the book in some way, cut them.
Stephen King likes to trim his books down by at least 10% in the second draft. That's a serious reduction in word count, but it works to make his prose so much better.
Remember: sloppy, wordy prose can sometimes come across as sloppy thinking. Trim down your writing, and your readers will thank you for it!