Favour sentences in the positive form
He is not very often on time. → He is usually late.
It was not a particularly enjoyable journey. → It was a rough journey.
Favour the active voice
Passive: My holiday to France will always be remembered.
Active: I will always remember my holiday to France.
Passive: Michael was attacked by the dog.
Active: The dog attacked Michael.
There are occasions when the passive voice is necessary, but the active is usually better in fiction writing. Just as an active character who is forced to make decisions under pressure is usually more interesting than a passive character who simply has a lot of things happen to them.
For variation, try placing the emphatic word in the sentence at the end
They used this metal for making swords, because of its hardness. → Because of its hardness, they used this metal for making swords.
Avoid dangling modifiers
A modifier describes another element in the sentence. It should clear which element the modifier is describing:
Searching the beach, Chloe tried to find her sunglasses.
The modifier ‘searching the beach’ clearly refers to Chloe.
However, with a dangling modifier the target is not clear:
With a sigh, the hat was returned to the rack.
We know a hat can’t sigh, so who returned it? We can usually work out dangling modifiers with context, but they are jarring to read.
Avoid run-on sentences
A run-on sentence has two independent clauses that have been pushed together rather than properly connected.
The current was strong he couldn’t cross the river.
Three options for correction:
Comma and conjunction (and, but, so…): The current was strong, so he couldn’t cross the river.
Semicolon: The current was strong; he couldn’t cross the river.
Full stop/Period: The current was strong. He couldn’t cross the river.
Avoid the comma splice
Like a run-on sentence, a comma splice pushes two independent clauses together, but the comma separating them is not sufficient.
The bunker was warm, they took off their coats.
The same three options for correction apply.
Use a comma before character names in dialogue
See the difference in meaning:
“I don’t know John.”
“I don’t know, John.”
There must be a comma before a character is directly addressed. Try to master control of the comma as you write; a common mistake is to assume it is only used when there is a natural pause in speech.
Be consistent with capitalisation
Research the capitalisation for titles in your novel, especially if you are dealing with the police, law courts, or any professions.
And see the difference regarding capitalisation for direct address:
This is for you, Mum.
This is for my mum.
Vary the pace
Over the course of a whole novel, a variation in the pace is essential. There should be high points and low points. Moments of calmer reflection, and moments of sudden intensity. The pace should build towards your novel’s climax, giving shape to your story.
Make the paragraph the unit of your writing, not the sentence
You should start a new paragraph when you start a new topic or change the time or location. And there should be a new paragraph every time a different character speaks. Consider starting a new paragraph for dramatic effect as well. It might be tempting to only focus on getting great sentences down, but you should work like an architect when it comes to building paragraphs, scenes and chapters.