1. Don’t use a Thesaurus—use a Dictionary.  

While a Thesaurus can come in handy, it is really only useful if you have a very good vocabulary to start off with and just need a garage to keep them all in. A dictionary, is more useful in writing because in the definitions, it often says other synonyms in the description, as well as decreasing the chances of having those slight differences a Thesaurus will give you. For example, a smile is different than a smirk or grimace, two examples in a Thesaurus for “smile.” If “smile” is going by a definition, it is, “Form one’s features into a pleased, kind, or amused expression, typically with the corners of the mouth turned up: “smiling faces”; A pleased, kind, or amused facial expression, typically with the corners of the mouth turned up and the front teeth exposed.” This gives you a lot more information to go off of, and could also give you some more ideas as a bonus.

2. Think about the tone of the piece.

If you are writing a piece in a particular tone, be careful of the words you use. Make sure your word choice matches what is occurring in your story. For example, if a house is haunted or “bad news” for the characters, you typically don’t want the house to be described as “welcoming and bright,” unless you are attempting a sort of “Hansel and Gretel” plot-twist. Also be aware of the tone of your piece—make sure the way you want the story to head is the same as your words are suggesting.

3. Don’t get too fancy with impressive words.

While having a big vocabulary is definitely an admirable trait, especially as a writer, it is a good idea to be wary of clunky, huge, or strange words when writing your story. Not only does it disrupt the flow of your piece, but often jolts the reader out of the story. There is nothing more strange than reading a word like “anathema”  when the reader could have said “taboo.” Keep in mind the fact that you don’t need to dumb down your story for the audience, but be aware of who your audience is, and the words most in that range are going to use or at least be aware of that word in their everyday lives. If you looked up “SAT words” on the internet, then there’s a good chance you are trying to make your story be more than it really is.

4. Use words that do more than just fill up space.

In a story, every word is important. So make sure you aren’t just paying attention to a word limit, and make sure the words do more than just state the obvious. “He was sad, disappointed and alone, sitting on the curb watching cars on the highway zoom past him,” does very little for the reader. “He sat by the concrete curb with hands covering his chapped lips, as he glanced at the passing cars with a glance common to beggars” says much more about the character.

5. Make sure you understand the connotation of a word.

A good example are the words “skinny” and “slender.” Both words mean almost the exact same thing, but generally speaking, “skinny” is more negative, and “slender” is more positive. Understanding the connotation of a word can make the story less confusing and more consistent.

Source: [link]