1. Join SCBWI (Society of Children's Book Writers and Illustrators). This organization is great for beginning and advanced writers. Their website has a members’ only area that includes information about writing, publishing, agents, etc. The bi-monthly bulletin gives you the scoop on current trends, editors, and lots of support.
2. Join a writers’ group if possible. If you can’t, consider one of the SCBWI on-line critique groups.
3. Attend a writers' conference. Gathering with other writers will jump-start your creativity. You'll return home with ideas buzzing through your head.
4. If you’re on the East Coast, check out Rutger's University One-On-One Conference every October. You have to submit a manuscript and then wait to see if you're accepted. (But don't feel bad if you don't get in - I attended three years in a row and then was rejected in the fourth year, after I'd sold Lasso Lou!) I consider this conference to be one reason I was published – I met an editor at Dial to whom I sent Lasso Lou. Before she left Dial, she passed it to another editor who passed it to another editor --- and on and on until it finally landed on Cecile Goyette's desk.
5. Write and write and write. Every day no matter what. The more you write, the better you’ll get.
6. Finish your project. It's amazing how tempting it is to start something, put it aside, start something else, then put that aside. Be disciplined. Remember: Don’t get it right, get it written.
7. Read the genre you’re writing. Read and read and read. The more you read, the more you’ll know what they’re publishing and how your work compares.
8. One final note that helped me: I retyped some of my favorite picture books. This exercise allows you to analyze the story. You'll see how many pages the manuscript would have been and how the author handled transitions. (It's easier to see this without the distraction of the pictures.)
Becoming a published author is one part talent and one part relentless, dogged determination. Good luck!