So many times, that's a question I hear from first time authors. Here's my answer, and you may not like it, but it's really the truth:
After you have announced your book to your friends via your email contacts, social media sites, and twitter, and have a short "signature" below your name in your email account, the best thing to do in the marketing arena is to write the next book and get it out there.
Yeah, I know that sounds weird, but I cannot emphasize this enough. Too many people with one book available are spending prodigious amounts of time trying in vain to influence sales, instead of writing the next book.
The thing is, the availability of multiple books/short stories/novellas is what seems to drive sales better than anything. And when someone spends all their time drumming up sales for their ONE book (and thus making a pest of themselves), what's the good of it if--when someone reads it and wants more--there is no more work available?
There IS no good that can come of that situation. After the reader exhausts their search engine capacities and their patience and doesn't find anything else by you, your name is then forgotten--once the distastefulness of the frustrating episode fades away.
DO make sure you have a blog that you update on some kind of schedule, if only once a month. Then you have an Internet presence, and you can give periodic updates on your work-in-progress (WIP).
DO make sure you have created your Author Page at Amazon (if your book is for sale there). Set it to post messages from your blog.
DO make sure you have created your Author Page at Goodreads. Set that one to post your blog messages also.
Then, go write the next book.