Here are a few tips for visiting cemeteries in search of your ancestors:
1. Get permission from the cemetery owners to visit if you're visiting a private cemetery. Keep in mind state laws regarding cemeteries on private land in order to know their rights and yours. For instance, Missouri requires that the property owner allow you reasonable access to the cemetery during reasonable hours of the day. (Link)
2. Get a long mirror to angle the sun towards the stone. This will help make the inscription clearer. Turn off your flash as that tends to only create a glare, and be prepared to write down what you see in case no amount of computer editing makes the photo reveal the whole inscription. (Note: I've found taking color pictures and then converting to black and white can help legibility.)
3. If you have to clean the stone in order to see the inscription, use water (the less chemicals in it the better) and a SOFT bristle brush. Gently wipe away the residue.
4. DO NOT use shaving cream to read the stone. Chemicals will only increase the weathering of the inscription.
5. Upload the photo to Findagrave for other relatives to find.