As long as the whole page fits on the scanner bed, then whole pages are the way to go. Back in the old days, when huge images didn't fit very well in a computer's memory, you'd be forced to subset things. Now, it's not really a big deal.

In terms of resolution, you're getting diminishing returns once you get beyond 300dpi, particularly if the original camera wasn't very good. The most important thing is that you carefully adjust the brightness/contrast settings of your scanner to get the most useful information out of the images.

For cropping and rotating, you may find that Picasa does everything you need. It's still a manual process, but you don't really need all the power of Photoshop. (If you *do* use Photoshop, the ruler tool will let you measure angles as well, so you can get the number you'll need for the rotate command.)

Exception to the rules: if you're scanning newsprint or anything that came out of a magazine, then the images have all been half-toned. If you scan at a low resolution, you'll get awful moire patterns. The solution is: (1) crank up the resolution until you can see all the original dots, (2) do a Gaussian blur with a wide enough radius to nuke the dots, (3) scale back down to a more reasonable size, and (4) unsharp mask to taste.