There is no easy answer to this question, nor simple equation. Marketing is an investment and that investment can be one of time (spent marketing on your own), money (having us or others do for you) or a combination of both. In terms of the ROI or direct pay off of ‘x’ marketing dollars/time spent equals ‘y’ books sold, well, we all wish we knew that answer or that it were that simple!
As to which marketing techniques produce the best results, that depends too on the specifics of the book and what the goals are. For the author who wishes to do book signings and events, a local outreach via a publicist service is likely the way to go. For the author who wants to connect with the most readers possible, a social media campaign will help them find fans and create a base of followers. For the author who wants reviews, creating a targeted database of likely reviewers, print and blog, is the way to go.
Fundamentally, marketing is not this one tactic or that one piece, it is much more an ongoing effort that will include multiple strategies to produce maximum results. These days marketing online = exposure and the more exposure the bigger your potential sales — it is simply that the easier and more often readers come upon you the more interested and likely they will be to buy. Exposure comes from third party content like press releases, reviews and awards; multi media content such as radio interviews and videos and book trailers; social media profiles (FB, LI, Twitter, Goodreads for example); and an author presence via an Author Website and Blog.
Each author needs to assess their personal goals and their available expenditure – be it time or money – for marketing and then work with us — or someone else — to develop the best possible marketing plan.