For those new this time around, a few things to remember.
And of course, doesn't hurt to have something to remind us for the rest of us.

Get your clothes ready. If bringing two sets (SUITS OR GTFO), 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?

Clothing Changes: Make sure you can do things quickly and easily. You don't want to be messing around for ages.

Weight: Don't over load, only bring what you can carry comfortably.

Transport: Try and stick to public transport, you can disappear into crowds and ques this way.