Mines goes along the lines of:
Hello Gents, Who are my front-row and replacements today?
Ok, well as you can see from my brilliant physique I was a front-row once too, so lets work together today. You know the drill - Crouch, Bind, Set as per usual. I'm looking for a nice long-arm bind, and no early engagements or pushing. If you have any questions about the Scrums, you are more than welcome to ask when appropriate (at Scrums).
Nine - with the Scrums.. I simply work with a double tap on the shoulder if I'm on your side. If I'm on the other my hand goes up. Is that clear?
Ten - you're responsible for offsides. If you want to check - just ask - at Scrums and Lineouts, I will be checking as well.
Who's my captain? .... Ok - In a minute I will call you over for the coin toss and a chat with the other captain. You've got xx minutes until kick off.
I know it errs on the long side, but I've been gradually cutting it down as I go. It will no doubt be shorter as the season goes on.