I've been reading each of my #BookADay picture books out loud in my office. I've read some before, and some I haven't. Reading them out loud emphasizes even more how IMPORTANT it is for aspiring picture writers to read their stories out loud.
If you find yourself stumbling over awkward phrasing or dull prose, then you know it's time to revise. Yes, the illustrations are going to add a lot to your story but if it's not an enjoyable readaloud, then it's going to be tougher to find a publisher.
I also encourage you to read other people's picture books out loud. If you're in a public place like a library or bookstore and don't want to disturb other people, then read silently. But HEAR the words in your head.
Also advised: be aware of pacing and page turns. More on this in a future post.