Hi Jess!
Make sure to check out the PSP forum here on SBB, lots of good questions and answers there.
Regarding 12x12, you can design at that size and print at 8x8. There are 8x8 albums that you can use too. You could also have them printed full size at a copy shop, but that may be expensive. I don't do 12x12 at this time (I do 8.5x11), but I do think a square layout is easier for composition than a rectangle. I sure some 12x12'ers on the site can chime in with more info.
Again, Welcome to SBB!