EDITING IS IMPORTANT!
Here is an editing checklist to get you started in the right direction and avoid basic grammar, spelling, and punctuation mistakes. Make a professional impression. Be competitive.
Spelling: Have you gone through your manuscript with spell check? "It's" and "its" need to be used correctly ("it's" is a contraction for "it is"; "its" is possessive).
Check other homonyms. Spell check doesn't catch them. (For example, "He peaked at her through the blinds and saw the peek of Mt. Everest.")
Grammar: Is dialogue is punctuated correctly? Are there run-on sentences, unintentional fragments? Do subjects and verbs agree in number? Are verb tenses consistent throughout? "That" and "which" used correctly?
What about pronoun references. Are they clear? Or confusing? Does sentence structure vary in descriptive or expository passages. What about word choice? Have you checked your basic facts?
Good resources for writers are: Chicago Manual of Style, Elements of Style, English Made Simple or Diana Hacker's Rules for Writers.