In most books, turning the page is what you do when you've run out of words on that page. A page break comes when the page is full up and there's no space for more words. In a picture book, turning the page is a specific act, part of the performance, and a page break comes at a carefully chosen place. There is usually space on the page for more words, but the writer has chosen to put a page break. Knowing where to put the page breaks is an important part of the skill of writing a picture book.
When the child (or reading-aloud adult) turns the page, the first thing they will notice is the new picture. Then they will read the words. (I know, you're the writer, you want them to see the words first - they won't. Live with it.) You can use the page breaks to reveal a surprise, to build up tension, to share a joke... But whatever you do with it, you must be doing something; there must be a good reason for putting the page break where it is.
You need to think about where the page breaks go when you are writing, but to check that you've got them right you need to make a dummy. A dummy is a little model of the book as it will finally be. Illustrators make dummies all the time, but not all writers bother. It is worth it - it's much easier to see how your book will be used and to understand the impact of the page breaks if you have a dummy. It's also very good fun as you get to mess about with glue and scissors and can claim it is real, hard work. You can even do some drawings if you like.
Most picture books have 12 working double-page spreads distributed over a total of 32 pages. To make a dummy, take 16 sheets of paper and fold them in half (I use A3 as it gives you A4 pages to work with, but you can make smaller ones). Number the pages, 1-32. Your text will start on page 6 (or 5 if you want to start on a recto - right-hand page). You can have 12 spreads, or 13 at a push. (There is some variation possible - you can use the end-papers, for example - but this is the basic scheme.) Now print out the text of your picture book and cut it up, then glue each bit of text onto the right page. If you're feeling artistic, or want to waste a bit of time, you can sketch roughs of the illustrations, but it's really not necessary. (You shouldn't send the roughs to the publisher unless you really need to show how something should look - or unless you are a professional illustrator. You really, really shouldn't get your child or friend to draw pictures and send them to the publisher - unless you are Joyce Dunbar, of course.)
Now you'll have a paper model of the book with the text on the right pages and a lot of blank space. If you are not very good at gluing, some of them might fall off, or be wonky, or actually be stuck to the table instead. No matter. As long as you have something roughly functional you can proceed. Turn the pages of the book and read the text aloud. (You must *always* read your picture book texts aloud as that's how they will be delivered.) Of course, you will listen to the sound of the words, the cadence, etc and correct the language as necessary - but what you need to concentrate on just now is what happens each time you turn the page. What is the nature of the event? Why is the page break there? Should it be there? Is it there just because you think there are enough words on the page? That's not good enough - your book is not sufficiently tightly structured if that's the case. Rewrite it.
Next look at where you move from a verso (left) to a recto (right) page. This is a lesser event, but it is still an event. There should be some logic to the split in the text. Sometimes the text might run straight across the spread and there is no split. There are some spreads like this in Polly Dunbar's Bubble Trouble, for instance. You need a strong spread if you are doing this. It will probably have a single line of text. Look also at where blocks of text should go on the page. You might have bits of text in several places - think about how you are dividing it up. Why does the block break there rather than somewhere else?
Think about what the pictures are going to show on each page/block. You can't have a page that has no potential for a strong picture, so you will need to change the text or page breaks if this is happening. You will probably have to make another dummy, or tear chunks out of your dummy and reglue them. (It quickly becomes a crumpled mess - make another.) But eventually you will work out where the page breaks need to go. When you are happy with them all, revise your manuscript and mark in it where page breaks occur - [page break] or [spread 3], for instance. (Notice that editorial instructions always go in square brackets.) Your editor will thank you for it - and also be less likely to break up the text in a stupid way. With luck, the illustrator will put you right if you've still managed to mess it up. You will look more professional if you can learn to get it right, integrating text, picture and the event of the page turn into a whole performance. Try to leave space not just for the illustrator's input but for the reader-aloud's input - space for sound effects, funny voices, oohs and aahs of surprise and suspense. That's why writing picture books is hard - just because it's short doesn't mean it's easy.
That was red herring last time, about work wear. Coming next... the writer's dress code