The first thing to keep foremost in your mind is that you are looking for a partner to help you get published and for some, to help with your writing career as a whole. Therefore, the rules you learned in Kindergarten apply! Be kind, courteous, and respectful.
Don’t be obnoxious and make crazy claims that this is the agent’s next meal ticket, that rejecting them is akin to missing out on a once-in-a-lifetime opportunity. You sound like an infomercial and won’t attract much positive attention. It also suggests you have a huge ego and no one wants to work with someone who already thinks they are fabulous and need to prove this to the world. It makes the process that much harder and the relationship very difficult to manage. Be realistic.
You are looking for an agent that you can develop a positive, healthy, friendly relationship with. A business partner of sorts ─ so act and choose accordingly.
Know the agent’s name! Do not spell the name incorrectly. Double, triple check it. How awful to spell a name wrong – it means you are careless and it sets the whole thing off on the wrong foot.
Don’t say To Whom It May Concern or Dear Agent. Did you not research this? It means you didn’t take the time to properly research the agency or the agents that work there. If you aren’t sure, phone the agency and ask whatever you need to know to get it right. If they aren’t helpful, perhaps you may want to reconsider doing business with them. After all, they need you to make their business model work.
Not having any name on the query (Dear Agent or To Whom It May Concern) indicates you are more than likely sending the query to many agents. Mass mail-outs don’t look good. Be choosy – or at least give the appearance of such.
NEVER say that an agent is going to miss out on the next bestseller if they don’t review your manuscript. Don’t say you’re the next Stephen King or Nicholas Sparks. Let the agent determine that. Nobody wants to work with a diva so keep diva-like behaviour to a zero minimum. This is a relationship you want to cultivate. Be likeable and real.
If you’re looking for a “Top New York agent” and actually say so in your query, make sure you query only the top New York agents! Don’t bug the small guys – it’s insulting and a waste of time because obviously you haven’t done your homework. I once had a writer say they wanted a top US agent. I’m Canadian – what part of Toronto, Canada did they not get???
Spelling and grammar. Please make sure your letters and synopses are error proof. It seems obvious but you have no idea how many come in riddled with errors. It says so much about you. It is what you’re trying to do for money so it represents you more than you think. If you can’t get a simple letter right, what are we to think of the manuscript?