For example, this is what I’m talking about:
"John ate pancakes. He looked over to see his wife enter the kitchen. Marsha smiled and kissed John."
Pretty boring, right? But how do you fix it?
The answer lies in varying your sentence structure and adding some more detail. Short, choppy sentences are another part of the problem here; they’re fine when used in moderation, and can easily be used to good effect for emphasis, but when used too often the writing starts to get boring, dry, and repetitive. Specifically, all three of the example sentences start with “subject + verb,” are short, and don’t have much description.
So, try changing the above to this:
"As light from the morning sun danced across his kitchen table, John speared a piece of his pancake breakfast and drew it to his mouth, chewing thoughtfully. Out of the corner of his eye, he saw Marsha, still clad in her nightgown and with a bright smile on her face, enter the kitchen. He looked up to greet her as she came over and kissed him good morning."
Much better now, right? This doesn’t mean you always have to write in overly flowery language – as I previously mentioned, Spartan writing can be used to great effect in a number of ways and situations. But varying your sentence structure is a must, because otherwise readers start zoning out and won’t be focusing on your story.