I know it is too late for the Page Turner contest, but for everyone out there who needs to write a synopis for a publisher or agent - I recommend The Sell Your Novel Toolkit by Elizabeth Lyon. There are not many books out there on how to write synopsis' for fiction (I have no idea why) but this one is for fiction and I have found it very good.
Of course, I should add that I have yet submitted one to a publisher or agent as my book is not done yet, nor have i submitted my 40 word snippet, for the same reason, but:
This is a trick that I found very helpful - write the premise of your book as you would see it in the TV Guide if it were a movie, ex: An Island Sheriff battles a Great White shark hautning his resort town (Jaws). Even practice on your favorite books and movies. Once you can do it in a single line, it is much easier to work with a longer length. Espcially one up to 500 words.
Another suggestion for a long (500 word) synopsis. Write a sentence for your inciting incident, one for your beinning, one for the middle, one for the climax/resolution, and be sure to include plot points (major turning points). Then build on that. And write in present tense.
Sorry I didn't think of this before the deadline.