In this section, I'll provide you with various raw scans which you can clean along with the lessons, or just practice on later. You get a finished example for one, but otherwise you're on your own. Feel free to email me with any questions. Having a scan near you to practice on while you go through the cleaning section might make things easier to understand.
Practice 1 - Explaination: Seperated them. For the right side, used the measure tool on the horizontal lines to rotate .26 counterclockwise. Cropped, resized to 690. Leveled the entire image 3 black, 247 white. Selectively leveled gutter & upper right area with the soft brush/gutter trick (size 45). (right side) For the left side, I rotated .57 clockwise, cropped, resized to 690. Leveled 235 white. Gutter shadow: on a large shadow like this, I used a size 300px soft brush. I had to nudge the selection and level the gutter in 3 steps. Finally, I manually cloned in the cut off black line to the bottom right. (left side). (Note that I didn't straighten the bent lines ~ I'm lazy.)
Practice 2 - You'll need to manually white-out quite a bit of dirt on this scan ~ leveling to get rid of it all will kill the scan.
Practice 3 - Leveling white anymore on this scan will kill it, but notice how the edges are dirty? Try selectively editing the edges (quickmask) to take care of this scan.
Practice 4 - Beware the huge gutter shadow...