Hal Croassum (Scriptforsale.com) has written a brilliant and thought-provoking article that potentially explodes the old myth than you need to grab the Script Readers attention in your first ten or twenty pages. After conversations with many producers he believes that it is the very first page which is key!
The article contains some great writing examples too.
Now cue me dusting off my scripts and re-analysing every first page! Yikes!