A dear friend of mine wanted to do something special for a couple’s upcoming 50th anniversary. The two surviving photos from their wedding were in pretty rough shape. She wanted to take lots of their photos and put them into a book. I got to help. Photo restoration takes infinite patience and attention to detail. But you can get pretty decent results.
Here is the original as scanned with my high resolution scanner. You might notice a few “issues”. Faded yellow, cracked, stained and oh, yeah missing a top right corner which cuts a lady’s face in two.
The first challenge is picking a place to start. Although I didn’t know it at the time, I should have immediately restored the whites to white and the blacks to black. I did it later and it worked out, but that wasn’t smart. I divided the picture into large areas; the groom, the bride, the background, and the big tear. Both the bride and groom were further divided into clothing, hands, face and hair, while I took the background into regions. As I worked on each of these, I did so on separate individual layers. That way when I messed up, and I did, I could a. not ruin the entire picture, and b. see and correct small manageable chunks. In Photoshop, you can also adjust the opacity of each layer separately, which is nice.
So I looked at the picture and chose to work on the groom’s suit. Broad surfaces, not overly detailed. In restoration, the clone stamp tool, the healing brush and layer masks are your standard weapons. In follow on blogs, we will drill down into the right ways and point out some “less right”—ok, wrong ways these can be used. Carefully masking out his outline, in order to prevent spill over, I reached the first signs of progress. 
I wasn’t ready to tackle the detail in the bride’s dress or hair yet, so I fixed the background. Matching random wall paper is harder than it looks, as is making the details in columns, lights and mirrors look “natural”.
After a few weeks, I felt my technique had improved enough to be ready to take on repairing the bride.
I left the missing corner for last as I had to decide what to do about the half a person in the picture. I finally made the hard decision that I didn’t have enough information to try and create all her missing features, so she disappeared into the wall paper. 
This is where the details become important and where the human eye can reveal more. We notice shadows, when they are out of place. So I had to create a suitable shadow of the bride on the now restored wall. The ability to use that layer opacity was very important here.
Finally, using curves and levels I fixed the overall tone of the picture and slapped on a new white border.
It took quite a while, but that was because I was learning as I went along. It gets faster and is worth the effort.