Let's start February Request month with what I like to call The Note. It's not a letter. Not an explanation.
When an agent requests some pages from you, 20, 50, 100, the whole thing, you attach (or paste in the email as instructed) the pages and add a note in the email.
Why do I repeat myself? Because some people use it as an opportunity to explain why I shouldn't be put off by the first few pages and if I just push through I'll see why it's so great, or where and when they came up with the idea, or that it's based on a part of their life that meant so much to them, or a million other little things that frankly, the agent neither needs nor cares to know.
You know the expression, you never get a second chance at a first impression? Or first impressions matter most? Don't forget, second, third, fourth, fifth impressions matter too. Let us fall in love with your manuscript and start seeing dollar signs before you let the crazy out of the bag. Go back to my "don't" list for queries (here and here). These will apply to almost every step of the process. Forever.
So, the Note.
Thank you for requesting (title). The (so many) pages are attached. I look forward to hearing more from you.
Ain't it purty? Of course, put your own spin on it. You don't have to use my exact words. The agent has already decided he/she is going to read your ms, so you just have to deliver and wait. You can add more personal notes if you have a deeper connection to the agent (for example, it makes me smile if a writer references a joke we've shared on Twitter), but again, not necessary. Most likely I'll forget who you are once I start reading the ms. You don't exist.
Why should it matter if you're professional or not since I don't care about you while I read? Because I care about you after I read. Or, in some cases, a very unprofessional writer can turn me off from reading their ms at all--because I already know I don't want to work with them.