the stand alone versions like Final Draft can be pretty pricey, but if you have no script writing experience formatting in Word can really slow you down.(I was typing them back before there was specialized software, in fact I seem to remember as a kid using a type writer for a few)
I have been tossing around buying this to make it easier, but I've been formatting my own for so long, I'm not sure it's worth the bucks.
Scriptwerx
Hope this helps.