Thanks to my friend Adam for pointing out this article to me: How to write effective emails.
I found a suggestion that I need follow faithfully:
If your message includes any kind of request—whether for a meeting, a progress update, a pony ride, or what have you—put that request near the top of the message and clearly state when you will need it. Do not, under any circumstances, assume that your overwhelmed recipient will take the time to sift through your purple prose for clues about what they’re supposed to be doing for you.
Good stuff.