I'm a television writer. I'm making my own kids TV show and trying to break into kids TV.
The best resource I've found is the TV Writer's Workbook. Tells you everything you need to know to write your own script, including how to make a great spec. Also gives some good industry advice.
I don't think the rules are different for anyone. They're just looking for spec scripts.
If you want to learn how to write a spec and improve your script writing in general, I strongly suggest this book:
http://www.amazon.co.uk/TV-Writers-Workbook-Ellen-Sandler/dp/0385340508
Consider reading this first, it's a great book written by an Emmy-winning writer/producer
ScriptNotes podcast. Literally everything you need to know and how to apply it. They even have this PDF called "The 100 Most Commonly Asked Questions About Screenwriting" that you can download for free here. Would post the actual file, but it's live, meaning it's updated periodically. So I recommend signing up.
If your interested in writing for television the TV Writer's Workbook is a must have. Simplifies everything and uses actual examples from the author's work ("Everybody Loves Raymond") to iterate points.
But most importantly, read. Everything. Especially screenplays. Like, a lot. Start with your favorite movies (or shows). Then go back and watch the film (or episode). What works? What doesn't? And why?
Good luck!