1) It is NOT a good idea to take 13" artwork and scale it down a lot in quark. Your service provider will not be happy with the amount of time it takes to RIP such a document. Best to either a) design the book, and tell the scan people to make photo A x size (you do know how to manually crop and scale, don't you?), or b) get all your good scans from the scan people and make copies, then resize them in photoshop. This way you still have nice big scans in case you need to make posters or something, but you aren't bogging down the RIP. General rule of practice: if scaling less than 85%, or more than 115%, do it in photoshop. I don't always follow this for little pix (<3") but for monsters like you are describing, phew!
2) To scale a box proportionally, <option-shift> while dragging the corner handles. To scale a box AND its contents proportionally, hold down <apple-option-shift> while dragging the corner handles.
3) To scale a picture proportionally into a picture box, <apple-option-shift-F> will scale it so it fits the width of the box. (<apple-shift-F> will make a picture scale to fit non-proportionally, but I have no idea why this would be useful to anyone.) Sadly, there is no command to make a picture box snap to match a photo's dimensions, I wish for this every day...
4) While I'm on a roll, you can also use <apple-shift-M> to center the picture in the box.
Just a few tidbits I got from reading the manual.
