Editing, self (books). When an author edits his or her own book. Not every writer can afford to pay for a professional edit, so those who can't may have to resort to self-editing. If you are a skilled writer with a clear understanding and good skills in spelling and grammar, that will help. Always read your manuscript aloud to pinpoint problem areas. You definitely want to run spell-check, but then be sure to print out the manuscript and run through it again, being sure to correct all spelling, punctuation, grammar, or typos. If you're new to writing for publication, you need to know that the old rule to leave two spaces at the end of a sentence has now been changed to one space.
If editing fiction, you will need to check some of these things: (1) Does your lead captivate the reader on the first page? (2) Follow each character individually through the story to be sure each has a unique personality, consistent and realistic dialogue. (3) Be sure you don't have too many characters, especially if they have not been appropriately introduced to the readers. Has each character's story been wrapped up at the end? (4) Check your descriptions. Too much too quickly? Are you overwhelming the reader with background information? (5) Check for dull or boring sections. What can you do to increase the pace? (6) Check for passive writing and change it to active. (7) Are your transitions smooth? (8) Do you show as much as possible—not tell? (9) Check length of chapters. Are some of them too long? (10) Does your conclusion wrap up all the plot points?
If editing nonfiction you will also start the same way as with fiction. In addition, check for these additional fixes: (1) Does the lead capture the reader's interest? (2) Have you given them a reason to read your book? (3) Have you illustrated your points with anecdotes or case studies the readers can identify with? (4) Have you included quotes from authorities, relevant statistics, history, or whatever fits your topic? (5) Have you double-checked all facts, quotes, or other information for accuracy? (6) Have you used unfamiliar or technical words—not defined—that the readers won't understand? Here are more tips to help with self-editing: http://www.techrepublic.com/blog/10-things/10-plus-ways-to-improve-your-writing-by-self-editing.