First, I’d always suggest you have a professional editor do your final check, but here are some tips for what to check when you’re doing the editing. You might want to use a program such as Autocrit to help you. And you might want to use an editing tip sheet to assist you. The following are a few tips that might help you.
Remember everything needs to be relevant and advance the story. If not relevant cut it and move on.
Omit or delete info that doesn’t add to the mood, character, or plot.
Show don’t tell. Avoid the passive voice.
Avoid negative sentences. The streets were not straight. Instead, the streets wound around the area.
Avoid cliches. You know - It was a dark and stormy night.
Emphasize the words you want to emphasize at the start or end of each sentence or phrase.
Check for word usage, frequently used words or repetitive words in follow-up sentences.
Check spelling and grammar. Use spell check but remember it’s not always correct. If you have specific grammar issues, for me it’s comma usage, research it before you start and have the explanation beside you to check out that specific issue when you spot it.
Em dashes like exclamation points should be used sparingly. Use an em dash because he’s cutting off his speech. Usually, a comma or a period will be sufficient.
An ellipsis indicates more of a slow speech pattern or a trailing off.
No spaces between the words and the ellipses.