Restoring old photos takes patience and sometimes a special knack for seeing the photo as it should be and as it was intended to be - and as it was photographed originally. Seeing the object clearly is simple for those who are interested in how their photos look.
What I mean is that sometimes a photo might be off centered and need to be straighten. Photo programs available on the market now have attributes for straightening photos. Lining up the corners as well as cloning and cropping techniques usually follow the straightening technique.
At times straightening a photo can be done by simply lining up with the corners with the corners of the scanner. To some that is not difficult to understand while others throw a photo on the scanner and whatever comes out is what they get.
Some techniques such as fixing cracks and torn places may take a more skilled hand and even a lot practice including some study. As you learn, remember to always work on a photo that can be saved over and over and never over-write your original. If at all possible start with a photo that is saved in high resolution so you can see the detail clearly.
If at all interested in photo restoration be sure and watch the videos that I have listed on this page. There are many tips given including constructive ways to restore and reconstruct broken and cracked pieces. These things are not learned over night and sometimes take a lot of practice - practice that most of us could use, yes, including myself.