If you are an aspiring author, then you’ve no experienced or are yet to experience the daunting challenge that is querying agents and editors about your manuscript.
Some resources for you:
Query Shark. Agent Janet Reid dissects and shreds the queries of many brave volunteers. She’ll show you what not to do and what really works.
Agent Query. Great resource for looking up agents, agencies, who represents who and comments as to who responds and who is a “no response means no” responder.
Absolute Write Query Forum. Find a willing volunteer to look at and critique your query letter. Note: You must have membership to the Absolute Write Forums but it is quick, free, and easy to get an account.