This is an excellent site, one of many that help aspiring (and published - not that I've made it there yet) writers. This site is also the inspiration for the blog I'm about to write.
Order! Who knew that the order of paragraphs was so important? Well everybody, of course! Every writer (big generalization, my English teachers can quit cringing) knows the importance of the order of paragraphs. Not necessarily. I'll be the first to step up to the plate and say that, more often than not, the order of the paragraphs in my writing are not always so precise. Case in point - my recent foray into Miss Snark's First Victim Secret Agent contest. I learned from that foray that the last paragraph of my 250 words, should have been my first paragraph. Second Case in point - the recent crit session of 1,000 word entries going on on MSFV right now: I critted one of the entries and noted that the fourth paragraph should probably be the first (see comment from that author here).
The order of paragraphs (speaking from personal experience only) is an easy thing to mess up. It is only through a second set of eyes that the reality (crap, bad order, need to fix, NOW) of the situation rises up and slaps the writer in the face. A simple change can make all the difference.
Why? Oh, let me tell you why!! My book shopping goes as follows: cover catches my attention, I read the back flap, the interior flap, and then flip to the first chapter and read (normally) the first page. If I'm not hooked by the end of the first page I normally put the book back down and look for something else to read. Now, I've passed on a few excellent books by doing this, and only discovered the error of my ways after someone gave me said book to read. Still, had the first page grabbed my attention more, then I might have purchased the book in the first place.
So, get your completed work out to whoever to take a read, especially the first chapter, the first 250 words, the first whatever that you, as a writer, are going to submit to an agent. Use Miss Snark's First Victim and enter the crit pool, do something, whatever, to make sure that the first impression of your blood, sweat, tears (loss of hair in my case, or a few pounds when I'm really in a good writing mode) captures the attention of future agent of choice.
In the end, a good opening doesn't necessarily mean a good book, but at least it might get your foot in the proverbial door of an agent, and possibly on to the path of success.