I talked previously about the most common mistakes that I see writers make. Mem Fox boiled it down to: "Would a child give a damn about this book?"
In the video, listen to the rhythm of her words; listen for the inflections and try and feel the suspense. Picture books, unlike novels, are an interactive experience. When I love a picture book, I don't just recommend to others that they read it; I want to read it with them. I want to read it to them. I want them to feel what I felt.
That's what giving a damn is.
With the right rhythm, tone, repetition, pacing, and narrative arc, you can do that - you can share directly with others the magic you feel as you read. You don't have to be a brilliant reader to do it; the writing and flow does it for you.
Read your picture books aloud before you submit; and have others do so, too. Listen to others read it to you. How do they feel after reading? Did they stumble? Was the rhythm and emotion and spark you felt when you put pen to paper conveyed back to you from the reading?
If not, you've got some work to do.
More read-alouds are on Mem's website.