The book covers here are unrelated to the topic. I just love them so I included them!
Finding an agent:
I don't give my agent's name to people I don't know really well--and even
then, I rarely do it. The agent/writer match up is an odd thing. Find the right
agent first time around if you can. Interview them honestly and represent
yourself honestly, too.... you are considering making them your business
partner. Make sure they LOVE your work, your career vision. It's good if
they like you a lot, too, and you like them. You want someone to be a partner
you can ask any question and get a real answer. You sign a contract, after all,
so begin this phase of your career seriously, don't rush it.
I am assuming that you are a good enough writer to begin the agent hunt. I
can't tell you how many people think they are...and aren't. If a bunch of agents
don't respond at all or several send your work back saying you aren't ready,
believe them, examine what they said and get to work. You can find places and
ways to learn how to write better in almost every town. Rejections are a
precious and free gift that agents hand to any aspiring writer: the unglossed
opinion.
Agents don't usually want new clients who echo what they are already
repping--at least not enough of an echo to make them feel redundant to
editors/readers/publicity people. All genres contain similarities...but you
wouldn't want to compare your work to mine (or anyone else's) in a sub letter.
If you describe your work well, the agent will be able to respond accurately
according to their current needs and what they see coming down the road....etc.
Some agencies have guidelines for sub letters...if they do, follow the
directions. They get hundreds/thousands....and they have asked for their
template to be followed in order to save staff hours. 
This SCBWI list might help.
