Becoming a better writer takes time, and a lot of practice. I've been writing professionally over a decade now ... and some of my pieces definitely still have room for improvement.
However good a writer you are, you'll need to spend at least some time editing: weeding out weak words and phrases, and making your writing as strong as it can be. Again, this takes time.
I've learnt over the years, though, that there are a few almost-instant ways to improve many pieces of writing:
#1: Cut Out the First Paragraph
Many writers (me included) tend to "warm up" at the start of a piece. Next time you write something, see whether you can cut the first paragraph or even the first sentence.
If the first paragraph isn't adding anything to the piece, taking it out will give you a stronger start -- whether you're working on a blog post, a freelance article, or a scene of your novel.
#2: Replace Over-Used Words
Repeating the same word too often (unless you're deliberately doing it for effect) can make your writing sound clunky or poorly edited. If you find you've used the same word several times within a few paragraphs, grab your thesaurus and look for some synonyms.
If there's not a good alternative, reworking the sentence or simply cutting it altogether can often work.
#3: Have a Proper Conclusion
When I review blog posts, this is probably the most common mistake I see: the post simply ends, without any sense of conclusion or rounding-off. This can feel oddly abrupt for the reader. Even adding an extra sentence or two can make a huge difference.
If you're writing short stories or novels, it's also crucial to make sure your ending isn't abrupt or unsatisfying. The last impression you leave readers with is the one they'll remember ... and they won't buy the next book if they feel cheated by your ending.
When you're in a rush, these three tips are some of the fastest, easiest ways to improve your writing. Give them a try today.