The number one most important thing to successful sales is...drumroll...
Tell a good story.
The second most important thing is edit the hell out of it professionally.
Some freelance sites or self pub mills charge between $500 - $2,500 and up....gotta spend money to make money sometimes. With all the dreck out there, your words need to stand out a lot more. Patience is very very thin.
The third most important thing is don't charge $19.99 for the digital edition of your 300k tome that reads like it was written in third grade English class and then tell everyone they should worship the ground you walk on because you wrote the book with pen and paper while in prison for a serious drug charge.
Local newspapers / advertising magazines are also a great place to start. Same with some radio stations and whatnot. I wrote a ten tips guide a while back that you can check out for more information.
Sometime soon I plan on talking to my old marketing boss and see if she has any other super special ideas. I know she specialized in mostly non/fiction and about 90% of our time was being hung up on by small 100 watt am radio stations. Apparently you can't sell a ghost book to an ultra conservative Christian talk show in Indiana. Who would have thought...but we did alright for JVP. Hell, he even got his own talk show for a while.
Most of what I did for those books consisted of going through the media directory and making probably around 300 cold calls a day to the marketing and PR managers. Then I would write press release after press release and fax them over the world. After that was said and done, I gave the UPS guy a hernia by sending out probably around 75 hardcover and ARC copies a day with all sorts of swag stuffed inside. These went to just about every major newspaper and book review magazine in the country.
There was an awful lot of ass kissing, some hand wringing, and a few people I wanted to kick in the teeth. We did all of this before social media and the rise of the internet becoming the juggernaut that it is today.