• Mirrors - By using a mirror to direct bright sunlight diagonally across the face of a grave stone, you can easily cast shadows in indentations which will makes inscriptions much more visible and easy to read. This method often brings out details that might otherwise be missed. A plastic full-length mirror works well. Ideally, the stone should not be taller than the mirror. If the stone is located in the shadows, you may be able to use two mirrors to help you reflect light. It might help to practice at home to determine the size of mirror that is needed and how to redirect the sunlight. But this is a safe way to get good photos without having to touch the stones. Note to photographers - If the sun is directly shining on the stone face, giving you too much glare, try using the mirror to throw light from the side and have someone block the direct sunlight. 
• Regular Lighting -  If you cannot wait until the sun moves into the correct position (at a right angle to the carved surface of the headstone), a flashlight or flood light will also work great., If working at night, please keep in mind that lights in a cemetery at night make people nervous and they tend to call the police (which, all things considered, is not a bad thing).
• Stick Your Head In A Bag Method - A variation on the regular lighting method, it is suggested that you bring a flashlight and a large paper ( not plastic) bag. Pull the bag over the stone, stick your head and the flashlight inside, and shine the light sideways on the inscription; you may be able to read an inscription you could not read before.
• Black Light Method - This one is a little more involved in that it requires that you bring some additional equipment and in some cases have a available power source. By using a 75 watt ( or higher) black light regular type or spotlight bulb in any lamp that casts light directly on the written message, the writing will stand out. Portable battery operated black light units can be found in most novelty or party shops, and as you get close to Halloween they can be found with ease in most department stores such as Wall Mart or Target. I found one in Atlanta at a greeting card / party supply chain store called Party City. Bulbs sell for about $3.00 and the battery operated units start out at around $8.00 and go up in price. Again, as with regular lighting,  if working at night, please keep in mind that lights in a cemetery at night make people nervous and they tend to call the police (which, all things considered, is not a bad thing).
• Tube Lighting - use a viewing tube, (a 2ft length of plastic drain pipe), held against the stone to prevent light entering, and then tilt the end of the tube touching the stone slightly, so that a little light enters, and then view the inscription through the tube
• Aluminum Foil Mirror- This is a variation on the use of mirrors as discussed above. By taking everyday aluminum Foil (Reynolds Wrap) which can easily be found at any grocery store or most convince stores and covering it over a piece of cardboard or some other hard substance, you can create a inexpensive alternative to a mirror that is non breakable, works just as good as a mirror and more importantly will not damage the stone in any way. The person who first suggested this method told the story of once needing some extra light and asking at a restaurant for a piece and found a piece of cardboard in a dumpster. Overall this method may not be the best way to go, but in a pinch it's worth a try. This method can also be used to add extra lighting to a stone for photography.
• Aluminum Foil Rubbing - An alternative to traditional wax or crayon type rubbings is that of aluminum foil & a damp sponge. Place foil on marker, dull side up so the sun doesn't reflect back into your eyes  Using the damp sponge press gently so as to not tear the foil around the carving or writing areas and instantly you have a 3-D impression of the marker that you can keep or ball it up and put it into your recycling bag. Also try reading the foil impression under different lighting situations. Sometimes it works better if the foil is placed on a tabletop under artificial light when trying to read it.
• Water - Just getting a stone wet can make the carvings stand out much more than when dry. It also adds to the enhancement if the sun light is at a good angle. Some stones don't photograph well, even when they can be read easily with the eye. Those stone really show well for photographs using the water method. The surface will dry much faster than the lettering. In most cases, the indented lettering will stay moist and dark which will enhance the image. In many cases, this will allow you to read the lettering fairly easily regardless of any fading that has occurred. We suggest that you carry several gallon jugs of water and a couple of large spray bottle to cemeteries. 
• Dirt - Grab a clump of slightly damp soil, (not mud) and gently rub the stone with it. After a minute or two the inscription will become very readable. After reading the stone, take a soft bristle brush and lightly brush it off.
• Hand Rubbing - It is sometimes possible on a uniformly colored stone surface, to lightly brush the surface with the palm of your hand, which raises a light dust (often dead lichen), and leaves the recessed inscription as a dark color. It is often worth a try!
• Photography Negatives -  By using either a digital camera and viewing the pictures in negative format, or scanning  regular prints into your computer and viewing using the negative (or reverse) option can be a highly effective way of reading worn stones. It just takes a little more time and steps to the process. 

Thanks to the wonderful members of the Cemetery-L Mailing list for providing many of these suggestions.