Get your clothes ready. If brining two sets, ensure they're both complete and ready.
Get your mask ready.
Get any leaflets, signs, cake etc ready.
Set your Alarms - we don't want you oversleeping.
Charge your cameras/phones etc
Prepare your drinks. e.g water.
Straws may be a huge help to the above as well.

Chance of rain, so I suggest waterproofing signs, and bringing some waterproof clothing as well.

KNOW THE BASICS. Make sure you can at least explain all of the basic problems and stories. Some people will know more, some won't, but everyone should at least know the basic information.

Anything I've missed?

*puts phone on charge, finds socks and empties camera memory card*

Those bringing cameras, I suggest emptying any current photographs from the memory cards - justincase is stolen by scifag - don't want to be accidentally giving away faces/details.