I've been writing for several years. I've researched and written a master's thesis. And believe me when I say that none of it compares with having to write topnotch query letters. Truthfully, I'd rather give birth through my nostril. Yet, there is a bright lining to this dismal cloud. I attended a writers conference recently and pitched to an agent. He thoughtfully read my query letter and replied, "Wow, this is a good letter." He then gave me permission to send him my MS.
It took all the fortitude and self-control I possessed not to snatch it from his hands and run through the crowd, waving it in the air and shouting, "I wrote a good query letter! I wrote a good query letter! Wa-hoo!" What a thrill to have succeeded at something that, for me, is painfully difficult.
To those of you who still find this task daunting, here are some things that helped me: keep trying no matter how tempted you are to give up. There is an excellent book by Terry Whalin, Book Proposals That Sell, and one especially for fiction writers, How to Write a Novel Proposal. Lastly, get a book on how to format letters, MS's and so on. The one I use is Formatting & Submitting Your Manuscript by Cynthia Laufenberg.