I mean this in two ways. The first way is literally read your work aloud as you write the words. Yes, you may draw some strange looks (I would not recommend doing this on a crowded train!) but if it doesn't sound right to your ears, then it won't look right to your eyes. Take breaths when you put commas in, be aware of how long your sentences and paragraphs are, and repeat.
Secondly, have a look at other works similar to yours. Note the language that the other author uses; does it sound right to you? Can you follow the sentences easily? You might learn something from those other writers, and with the Internet, chances are you can reach them directly for advice.
I said last week that critique is critical. Critiquing your own work is hard, but if you can demand better from yourself, your work will reflect that.
Don't put your work down; if you've written a book or even an essay, you should celebrate that. Just keep in mind what you're writing and whether you could say something in a different way. For example, instead of "the dog ran quickly through the park", try saying something like "the dog streaked over the lush green grass like a comet."
From there you can add more details like the colour of the dog's fur and why it was running in the first place.
You're book says a lot about what your like as a person. Hang on, something is not quite right with that sentence. It should say: your book says a lot about what you're like as a person.
Mistakes like these are easily done. Even authors who have sold thousands of books worldwide can make them. Make sure you know whether you need "you're" or "your"; "there", "their" or "they're".
I'll go through these on a later blog post, so keep your eyes peeled! (See what I did there!)
There is no shame in asking for help. Even you just ask a friend to read over an essay, their advice could potentially be the difference between a B and an A.
Authors in particular need to ask for help. Editing your own work is hard and can still leave errors behind. Getting a fresh pair of eyes to go through your work is vital to perfecting your novel. Don't forget to check out my last post on this.