Advice from Greg Johnson
Greg Johnson of Wordserve Literary Agency describes the extra mile he recommends for pre-published novelists.
Join a critique group, listen and apply other's input.
Attend conferences and pitch your idea.
Attend workshops.
The next are tougher, but he knows the game:
Exchange your completed manuscript with as many as ten people (not all have to be writers, but should be interested in fiction and able to give constructive feedback).
Hire a content and copy editor ($).
More detailed advice: http://www.wordserveliterary.com/contact%20uspt1.html