I would recommend making it slightly more vague in some ways(never say why you need/want leave) and more specific in others(be extremely explicity about the dates/times/length of time. And example:
I would like to request leave for the day of Thursday, November 24th 2014.
This does a couple of things - highlights which day of the week(so there are no confusions about timed deliverables), highlights how long(one day) and gives the specific date. In fact this could be abstracted to a template like so:
I would like to request TYPE_OF_LEAVE leave for AMOUNT OF TIME on START_DATE through END_DATE
TYPE_OF_LEAVE = Paid, ETO, Unpaid, etc
AMOUNT OF TIME = a rough estimate of how long you are planning on being off
START_DATE, END_DATE = the official range you are requesting off
If you do want to give more information then add something like "I will/will not be available during this time via email/phone/carrier pidgeon." is about a far as you should go. Why? If you have an embaressing or private reason for taking leave and you have gotten in the habit of saying why you want/need leave then when you don't want to say why(surgery, job interview, whatever) then you're in the position of lying which almost never turns out well.