Familiarize yourself with the short story format. Read short stories by Joan Didion, Jorge Luis Borges, John Cheever and other noted short story writers. Get a feel for the pace of writing prose in a compact form. Short stories usually contain few characters, present a clear theme and make every word count. Take it from eminent short story writer Stephen King, "If you don't have time to read, you don't have the time or the tools to write. Simple as that."
Carry a journal or notebook wherever you go. When inspired with an idea, such as a story plot, a line of dialogue, the name for a character and so on, write it down. Inspiration can strike anywhere---you might observe something interesting or overhear a mysterious snatch of conversation that could lead you to a story. Award-winning novelist and publisher Barry Hoffman says, "I'll make notes while I'm driving or play with dialogue in my mind while going for a walk."
Plan the format of your book of short stories. Do you want the stories in your book to share a theme, genre or style, or would you rather assemble a random collection? Will you be writing horror stories or comedic essays? If you decide to go with a theme, choose the types of stories you will include and the order you want them to appear. If you decide on an assorted collection of short stories, choose the order you want the stories in.
Write, write and write some more! Create a writing schedule and stick to it. Set aside time to write every single day. Columbia University's Graduate School of Arts and Sciences advises, "Writing every day contributes to continuity of your thinking and generating the ideas you need to write. Your mind will function differently when you write every day."
Understand that writing is rewriting. Once you have written a story, go back and revise it. Check it for spelling and grammatical errors. Read it over and over again to see if it "sounds" right. Read your stories out loud to test whether the story reads well and the dialogue rings true. One of Elmore Leonard's ten rules of writing is, "If it sounds like writing, I rewrite it." Hire a freelance editor if you want a professional opinion.
Create title pages. Create a page with the title of your book and your name as well as title pages for each of your stories. Organize your book according to your plan, and include the title story pages to distinguish each story.
Decide what to do with your completed manuscript. You can send it off to publishers or literary agents, you can pay to self-publish professionally bound copies that can be distributed to book stores and sold online, or you can take it to a copy store and have your single copy bound in a variety of ways. Another creative way to complete your book of short stories is to bind and cover it yourself.