There is no shortcut to being published.  It's not like algebra, where 2 and 2 always equal 4.  Becoming a published author is a process that requires talent, discipline, storytelling sense, the ability to craft words carefully, commercial appeal, and blind luck.  None of these things had ever been quantifiable.  The luck, in particular, is extremely hard to predict.  

The first rule is to sit down and write the best book you are capable of writing.  There is no substitute in this business for a finished manuscript.  Once you have that, there are things you can do to swing the odds in your favor.

1. Read broadly in the genre you wish to write in.  This gives you some idea of what editors are buying.
2. Seek knowledgeable criticism of your manuscript and listen to any comment that reoccurs frequently.  One critic can be wrong, but if six people tell you your plot is too far-fetched, it just might be too far-fetched.
3. Have a good proof-reader check the manuscript for presentation, typos, and stupid mistakes.  These are easy to catch, and it's a pity of leave them in when they make your work look unprofessional.  
4. Research the market before you mail your book.  Don't send a hot romance to a religious press, for example.  Don't send a 50,000 word contemporary to a house that doesn't publish short fiction.  Go to a bookstore, and jot down the publishers of recent releases that are similar in length and flavor to your work, then target those houses.  Make a quick call to the house (phone numbers are in Books In Print) to verify the spelling and title for any targeted editor the day you mail any manuscript.  People change jobs frequently in this business and it pays to double check this stuff.
5. Don't take rejection personally.  This is a business.  Editors are as different as readers, one loves Ibsen, another Jackie Collins.  Rejection can be a matter of reading taste, a glut of similar stories, a lack of room in the list, or any of a number of things that have nothing  to do with whether or hot your work is publishable. 
6. Watch bestseller lists and try to read any books that do exceptionally well in your genre then see if you can figure out why they are successful.  The author may have tricks you can't use, but the habit of reading critically carries over into your editing your own prose, and makes you a better writer.
7. Study the craft of writing.  Books like Cheney's GETTING THE WORDS RIGHT, Dwight Swain's TECHNIQUES OF THE SELLING WRITER, Orson Scott Card's CHARACTERS AND VIEWPOINT, and anything by Lawrence Block can teach you a lot about the business and practice of writing.  
8. Enjoy the process.  If you are destined to be a published writer, the months and years spent working on early manuscripts may be the last time you ever have the luxury of writing for the love of it at your own speed.  As soon as you sell, things like deadlines, the sales department's mindless prejudices, the editor's input, and so on become a part of your work.  You will, trust me on this, look back with nostalgia on the days when the only person you had to please was yourself.