For the love of all that is holy, if you're going to use PhotoPass,
WRITE DOWN YOUR PHOTOPASS CARD NUMBER!
I say this from experience.

The one and only time I leave DH in line with the kids and the PhotoPass to see the Incredibles, he tells me, a half hour later, that our PhotoPass might not be ours.
You know that feeling you get when you ride TOT? Yeah, imagine that, only ten times worse.
I hadn't written down our number and had to make the mad dash back to The Darkroom to ensure that we had gotten OUR card back. Thank goodness we had and I immediately jotted down our number in case it happened again.
So my tip?
WRITE DOWN YOUR PHOTOPASS NUMBER!!