Blake Snyder called his book "The last book on screenwriting you'll ever need"
I don't know about that. Its always good to check out other books but this is a great resource for aspiring screenwriters.
http://www.blakesnyder.com/ (the last website on screenwriting you'll ever need)
Save The Cat and sequel Save The Cat Goes To The Movies give you an exact guide for your script structure as well as key pointers:
Join us Snyderphiles. If you don't want to buy the book, shame on you, buy it anyway. In the mean time, I have included the most important part: The Beat Sheet in the link above.
Don't give up on your screenplay and don't let your cat die, OK?
Kelly Sallaway,Producer for Kellan Media is tasked with the care and feeding of the Kellan Blog.