This article from Tim Grahl contains the best reasoning I've seen for why you should begin your author platform and developing your networks as soon as you begin to write seriously and not after the manuscript is finished and the decision to publish is made. It explains why I have seen so many writers succeed with the former (eg Georgie Donaghey and Katrina McKelvey) and many more fail with the latter (do you remember our Kickstarter friend?). http://timgrahl.com/when-should-you-start-marketing-your-book/?utm_content=buffer36c1d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer
Now for some more good stuff from Chris Wilson, this time about writing introductory letters and emails in order get a response from decision makers (producers, art directors etc). The comparison between the two letters, one bad, one good, is instructive and easily transferable not only to seeking paid creative projects but also to the business of writing query letters (although for query letters a 'call to action' is a no no). http://us6.campaign-archive1.com/?u=e697248f247d94623b1b5bb8a&id=ecdb59b2f8