Both of these links provide clear examples of the right way and the wrong way to go about these two important tasks.

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

There is something that makes a successful illustrator stand out from the rest of the wannabees, and Wendy Martin has put her finger on what that is: http://wendymartinillustration.com/wordpress/2014/03/14/location-location-location/ . If you take your main character/s out of the picture, can the background hold its own? To see how important this is, visit @cillustrators and scroll through the illustration work they feature.

She also has five ideas for moving out of your illustrator comfort zone: http://wendymartinillustration.com/wordpress/2014/01/14/portfolio-builder-jump-your-comfort-zone/ . Commit yourself to quarterly promotional mailings. Enter illustration competitions. Do some guest blogging. Prepare a portfolio for a market outside children's books. Have a go at sharing your passion through teaching.

Here is a useful list of things independent authors can do to increase their chances of success, together with reasons why they can make such  difference: http://www.richardstephenson.net/?p=85 . The bullet points are: recognize the monetary limits of your genre; hire an editor; use proof readers; get a professional book cover; begin by going exclusively with Amazon and KDP Select; use social media; master the art of advertising; interact with your readers; when you receive praise, ask for a review; and advertise your other works at the end of your book. 

Some take-home quotes from Richard Stephenson's article are:
"In terms of paid advertising, my primary piece of advice is to never gamble what you can’t afford to lose because there is no guarantee that you will get it back." 
and " Get your name out there whenever you can. It might seem like a complete waste of time that gives nothing in return at first, but plant those seeds early on and they will bear fruit in the future."

Both of these apply equally to writers and illustrators, and indeed to any other kind of creative entrepreneur. 

Dealing with rejection letters is something writers and illustrators face on a regular basis. For truly sage advice on this matter visit: http://editorialanonymous.blogspot.com.au/search/label/The%208%20Rules%20of%20Rejections. "Most rejection letters mean nothing. Nothing. (Except that you can cross that publisher/agent off the list.) The only possible exception to that rule is specific, constructive criticism. If it is not specific, it means nothing. If it is not constructive, it means nothing. If it is not criticism, it means nothing."

This next article is a brilliant list of common pitfalls that writers and illustrators face in developing their creative careers: http://www.artsbusinessinstitute.org/blog/10-mistakes-that-stop-your-creative-business-in-its-tracks/. Take a few moments to review your current creative practice against these 10 very common mistakes: No plan; Lack of persistence; Working in isolation; Not understanding your audience; Being unclear on your message; Playing it Safe; Not understanding your sales cycle; Having little or no online presence; Lack of marketing strategy; Failure to follow up or follow through. Choose one to work on, and see how big a difference it makes.

Writing the first draft of your story is actually the easy part. For an infographic flow chart on what comes next, this featured link is excellent: http://www.adweek.com/galleycat/publishing-a-novel-infographic/98591
If you are just starting out, it will save you from some novice mistakes. If you have experienced the querying process, it will assure you that you are not alone, and you might even experience a chuckle. 

James Foley, a Perth based illustrator, http://jamesfoley.com.au/ frequently gets requests from TAFE students. They always ask him what the work of a professional illustrator looks like. So he decided to write a blog-post about it http://jamesfoley.com.au/2015/03/04/how-to-survive-as-an-illustrator-advice-for-a-student/ . For James the thing that really started his career on the right track was joining SCBWI and learning about the industry from others who already had a degree of success. However the bulk of his income comes from doing talks and workshops. It took 6 years of having a day job before he could go full time with illustration. But that is only an appetiser, the blog-post has much more.