Here is a recent question I got from a reader. Thanks for allowing me to use your question to help others, Patrick! I hope it helps you, too.
Hi!
You’re busy, so I’ll try to be quick! I’m a teacher who writes and also considers myself an artist, though my training on visuals is in video production (wow, I sound very eclectic). My question is, as an unpublished (well, sorta – put out a book last year with a charity that donates books to kids in my area – non-profit) author who also wants to illustrate, how do I submit a manuscript and art/PB dummy so that it’s taken seriously in the slush pile? I know that many first published’s are done by writers and then illustrated by bigger names to create more of a following to the author’s work, but like all good picture books, my stories are told through words with a lot revealed through images. Any thoughts are helpful – there are few clear answers out there. THANKS! 🙂
Patrick
Dear Patrick,
I know it often feels like there is so much information that it becomes overwhelming and it’s the same as having no information at all! But you just need to know where to look! Here are some suggestions:

• One place to learn about the business is SCBWI, aka the Society of Children’s Book Writers and Illustrators. It’s a fantastic and very valuable organization that has been answering these kinds of questions (and the prayers of the prepublished, including me when I was starting out) for 40 years! There are national, regional, and local conferences you can attend, and they have a great site and bulletin chock full of info.
• Another place to learn is through my free podcasts, where I often interview authors, illustrators and other people in the business. We talk about the craft and business of children’s books and there are lots of conversations where I learn things too! In fact, yesterday’s episode with Emma Dryden answers almost every question you have above.
• There are tons of books out there on writing and revision, like this one by Harold Underdown or  this one by Aaron Shepard and this one by Cheryl Klein.
• Pretty much everything you ask is also in the How to Make a Smart Dummy tutorial on this page. It’s an approximately 10 minute video tutorial that shows you dummies by different authors and illustrators, you can see how to do thumbnails, what to include and what not to include, and is a more visual way to learn about making a dummy. (you’ll have to scroll down a tad)!

But I will answer you here, too.
To be taken seriously, you need to take your work seriously. That means educating yourself on how the business works, so that when an editor gets your dummy or manuscript, it looks professional, and looks like you’ve done your homework (more on this in the podcast with Emma, too). It means you need to check and double check your spelling, grammar, and punctuation. It means you know that you don’t paginate, or include art notes because you trust that the editor will bring all his or her talents to the reading.
That is how you get taken seriously. Take yourself seriously. Do your research, soak up all you can learn about this wonderful business, and write well and often!