Taking pictures and other medias to document a PCB is usually the first step in the process.
The minimum requirement is a digital still camera, the higher resolution the better. Just to give you some indication I have a 5Mega pixel camera and it's more than enough; let's say that every modern camera is good for our porpouse.
What is not good is a phone camera because usually it has got a way inferior resolution, a very bad contrast range and it's very difficult to keep it steady.
The first step is to take pictures of the PCB; prepare a place that will become your "studio", I like very much to take pictures of PCBs while they are vertically laying against a wall, some other prefer to take pictures with the PCB flat on the ground. In both cases use a monocolour, flat, opaque, neutral background; avoid plain white, it will reverberate back to the camera; avoid multicolours tiles, they usually shine and tend to alterate camera contrast; eventually you can use for your background a brown paper of the kind used to wrap up delivery parcells.
If you take pictures of a vertical PCB use a tripod, even a very small one to hold the camera; if you do not have a tripod, put the camera at the same heigh of the PCB, possibly resting over some books with a rigid cover; do not hold the camera in your hands because it's much more easy to "move" the picture.
If you take picures of an horizontal PCB use a tripod again, of the kind with the tilting head to hold the camera horizontal as well; if you do not have a tripod hold the camera in your hands, tray to stay over the PCB with your legs slightly open, and hold your breath while taking the picture; if possible try to lay against a wall, this will help you to remain steady.
The lighting of your "studio" is very important: the best possible source of light is the sun, but it's not always available, therefore a very good alternative is a couple of halogen lamps of about 300-500W, illuminating the PCB from a few meters away. The very important thing is to avoid direct lighting of the PCB, but to illuminate it with light reflecting out of the walls and ceiling, resembling as much as possible the natural ambient light. NEVER use the flashlight incorporated into your camera, because it will reflect back from the PCB and "blind" the picture.
A good thing is to clean the PCB from dust before taking pictures; if the PCB is very dirt, at least clean the surface of the ICs with a soft slightly humid cloth, so that markings and labels are clearly visible.
Remember to take pictures of both sides of the PCB (components and solder), if the PCB consists of different boards packed one over the other, separate them and take pictures individually.
If the PCB is working, it's now time to go to step 2: taking pictures of the game in action.
So connect the PCB to your test rig, fire it up and let the game run for a few minutes so that your monitor gets to the right temperature. Calibrate your monitor to have a good full picture of the game, with warm saturated colors, and make sure that the full image is shown within the borders. Now shitch off all ambient lights so that the monitor itself is the only source of light, and holding the camera in your hands keep as steady as possible and take pictures of the game at boot up, at title screen, at intro and attract mode, and during game as well. It is not important to have them at very high resolution, on the contrary 640x480 or 800x600 are more than good. Sometimes it's a good idea to film a few seconds of the game, especially if the game is extremely rare and there are no movies of it available on the net. A similar thing is valid for sounds: if the game is extremely rare or very old and there are no sample available, record the sounds of the game. There are 2 ways to do it: with a microphone or directly connecting the PCB to your computer sound card. With a microphone you get a lower quality samples, possibly degradated by the quality of the speakers on your test rig and by the quality of the microphone itself; but it's a simple method and it's higly recomended if you do not know how your PCB works. Connecting the PCB directly to your sound card requires a little of electronic knowledge, a soldering iron and a clear idea of what you are doing; if you do not know how to do it DO NOT DO IT! otherwise you will end up with a broken PCB and a broken sound card.